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 $30.98   5.211%   $32.5944   $32.59   $32.60   $32.60  
  Purchase #2 $122.94   7.457%   $132.1076   $132.11   $132.10   $132.10  
  Purchase #3 $169.29   6.330%   $180.0061   $180.01   $180.00   $180.00  
  Purchase #4 $236.29   8.437%   $256.2258   $256.23   $256.25   $256.20  
  Purchase #5 $119.65   10.250%   $131.9141   $131.91   $131.90   $131.90  
  Purchase #6 $154.29   7.191%   $165.385   $165.39   $165.40   $165.40  
  Purchase #7 $120.63   5.113%   $126.7978   $126.80   $126.80   $126.80  
  7 purchase totals = $954.07       $1,025.0308   $1,025.04   $1,025.05   $1,025.00