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 $205.42   4.258%   $214.1668   $214.17   $214.15   $214.20  
  Purchase #2 $64.46   11.170%   $71.6602   $71.66   $71.65   $71.70  
  Purchase #3 $23.33   6.310%   $24.8021   $24.80   $24.80   $24.80  
  Purchase #4 $244.58   7.310%   $262.4588   $262.46   $262.45   $262.50  
  Purchase #5 $205.32   3.843%   $213.2104   $213.21   $213.20   $213.20  
  Purchase #6 $193.86   13.299%   $219.6414   $219.64   $219.65   $219.60  
  Purchase #7 $25.91   8.126%   $28.0154   $28.02   $28.00   $28.00  
  7 purchase totals = $962.88       $1,033.9551   $1,033.96   $1,033.90   $1,034.00