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 $68.34   8.467%   $74.1263   $74.13   $74.15   $74.10  
  Purchase #2 $232.31   3.560%   $240.5802   $240.58   $240.60   $240.60  
  Purchase #3 $144.49   12.369%   $162.362   $162.36   $162.35   $162.40  
  Purchase #4 $103.53   9.648%   $113.5186   $113.52   $113.50   $113.50  
  Purchase #5 $188.83   12.380%   $212.2072   $212.21   $212.20   $212.20  
  Purchase #6 $70.95   7.634%   $76.3663   $76.37   $76.35   $76.40  
  Purchase #7 $131.79   9.380%   $144.1519   $144.15   $144.15   $144.20  
  7 purchase totals = $940.24       $1,023.3125   $1,023.32   $1,023.30   $1,023.40