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 $50.67   5.863%   $53.6408   $53.64   $53.65   $53.60  
  Purchase #2 $130.80   12.643%   $147.337   $147.34   $147.35   $147.30  
  Purchase #3 $172.49   3.188%   $177.989   $177.99   $178.00   $178.00  
  Purchase #4 $218.92   11.539%   $244.1812   $244.18   $244.20   $244.20  
  Purchase #5 $156.96   6.682%   $167.4481   $167.45   $167.45   $167.40  
  Purchase #6 $119.73   3.831%   $124.3169   $124.32   $124.30   $124.30  
  Purchase #7 $95.62   12.452%   $107.5266   $107.53   $107.55   $107.50  
  7 purchase totals = $945.19       $1,022.4396   $1,022.45   $1,022.50   $1,022.30