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 $174.58   10.707%   $193.2723   $193.27   $193.25   $193.30  
  Purchase #2 $223.40   10.475%   $246.8012   $246.80   $246.80   $246.80  
  Purchase #3 $165.34   11.438%   $184.2516   $184.25   $184.25   $184.30  
  Purchase #4 $92.39   10.364%   $101.9653   $101.97   $101.95   $102.00  
  Purchase #5 $65.69   10.283%   $72.4449   $72.44   $72.45   $72.40  
  Purchase #6 $58.32   6.294%   $61.9907   $61.99   $62.00   $62.00  
  Purchase #7 $246.51   5.519%   $260.1149   $260.11   $260.10   $260.10  
  7 purchase totals = $1,026.23       $1,120.8409   $1,120.83   $1,120.80   $1,120.90