Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $190.88   5.663%   $201.6895   $201.69   $201.70   $201.70  
  Purchase #2 $102.96   13.228%   $116.5795   $116.58   $116.60   $116.60  
  Purchase #3 $208.49   3.753%   $216.3146   $216.31   $216.30   $216.30  
  Purchase #4 $215.99   3.482%   $223.5108   $223.51   $223.50   $223.50  
  Purchase #5 $239.68   9.814%   $263.2022   $263.20   $263.20   $263.20  
  Purchase #6 $187.48   9.751%   $205.7612   $205.76   $205.75   $205.80  
  Purchase #7 $126.73   11.816%   $141.7044   $141.70   $141.70   $141.70  
  7 purchase totals = $1,272.21       $1,368.7622   $1,368.75   $1,368.75   $1,368.80