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 $85.29   7.811%   $91.952   $91.95   $91.95   $92.00  
  Purchase #2 $234.71   12.753%   $264.6426   $264.64   $264.65   $264.60  
  Purchase #3 $214.97   13.628%   $244.2661   $244.27   $244.25   $244.30  
  Purchase #4 $244.84   6.211%   $260.047   $260.05   $260.05   $260.00  
  Purchase #5 $85.28   8.200%   $92.273   $92.27   $92.25   $92.30  
  Purchase #6 $43.54   9.728%   $47.7756   $47.78   $47.80   $47.80  
  Purchase #7 $105.52   8.746%   $114.7488   $114.75   $114.75   $114.70  
  7 purchase totals = $1,014.15       $1,115.7051   $1,115.71   $1,115.70   $1,115.70