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 $72.64   4.464%   $75.8826   $75.88   $75.90   $75.90  
  Purchase #2 $150.31   9.483%   $164.5639   $164.56   $164.55   $164.60  
  Purchase #3 $62.68   13.113%   $70.8992   $70.90   $70.90   $70.90  
  Purchase #4 $201.46   4.435%   $210.3948   $210.39   $210.40   $210.40  
  Purchase #5 $235.90   4.347%   $246.1546   $246.15   $246.15   $246.20  
  Purchase #6 $214.83   13.810%   $244.498   $244.50   $244.50   $244.50  
  Purchase #7 $34.79   5.559%   $36.724   $36.72   $36.70   $36.70  
  7 purchase totals = $972.61       $1,049.1171   $1,049.10   $1,049.10   $1,049.20