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 $163.97   11.340%   $182.5642   $182.56   $182.55   $182.60  
  Purchase #2 $216.72   7.320%   $232.5839   $232.58   $232.60   $232.60  
  Purchase #3 $94.80   9.250%   $103.569   $103.57   $103.55   $103.60  
  Purchase #4 $75.60   3.623%   $78.339   $78.34   $78.35   $78.30  
  Purchase #5 $98.67   12.239%   $110.7462   $110.75   $110.75   $110.70  
  Purchase #6 $51.60   13.599%   $58.6171   $58.62   $58.60   $58.60  
  Purchase #7 $103.51   4.506%   $108.1742   $108.17   $108.15   $108.20  
  7 purchase totals = $804.87       $874.5936   $874.59   $874.55   $874.60