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 $182.69   7.467%   $196.3315   $196.33   $196.35   $196.30  
  Purchase #2 $34.38   3.669%   $35.6414   $35.64   $35.65   $35.60  
  Purchase #3 $49.54   10.398%   $54.6912   $54.69   $54.70   $54.70  
  Purchase #4 $92.57   10.507%   $102.2963   $102.30   $102.30   $102.30  
  Purchase #5 $71.35   7.608%   $76.7783   $76.78   $76.80   $76.80  
  Purchase #6 $212.40   7.492%   $228.313   $228.31   $228.30   $228.30  
  Purchase #7 $34.49   12.165%   $38.6857   $38.69   $38.70   $38.70  
  7 purchase totals = $677.42       $732.7374   $732.74   $732.80   $732.70