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 $58.81   8.146%   $63.6007   $63.60   $63.60   $63.60  
  Purchase #2 $142.39   5.170%   $149.7516   $149.75   $149.75   $149.80  
  Purchase #3 $245.96   5.440%   $259.3402   $259.34   $259.35   $259.30  
  Purchase #4 $181.35   12.669%   $204.3252   $204.33   $204.35   $204.30  
  Purchase #5 $152.65   13.534%   $173.3097   $173.31   $173.30   $173.30  
  Purchase #6 $7.46   11.173%   $8.2935   $8.29   $8.30   $8.30  
  Purchase #7 $165.42   7.115%   $177.1896   $177.19   $177.20   $177.20  
  7 purchase totals = $954.04       $1,035.8105   $1,035.81   $1,035.85   $1,035.80