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 $40.58   13.565%   $46.0847   $46.08   $46.10   $46.10  
  Purchase #2 $195.47   8.456%   $211.9989   $212.00   $212.00   $212.00  
  Purchase #3 $238.37   7.605%   $256.498   $256.50   $256.50   $256.50  
  Purchase #4 $247.53   9.152%   $270.1839   $270.18   $270.20   $270.20  
  Purchase #5 $41.45   5.569%   $43.7584   $43.76   $43.75   $43.80  
  Purchase #6 $174.98   8.334%   $189.5628   $189.56   $189.55   $189.60  
  Purchase #7 $58.70   9.418%   $64.2284   $64.23   $64.25   $64.20  
  7 purchase totals = $997.08       $1,082.3151   $1,082.31   $1,082.35   $1,082.40