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 $87.93   10.258%   $96.9499   $96.95   $96.95   $96.90  
  Purchase #2 $50.26   4.195%   $52.3684   $52.37   $52.35   $52.40  
  Purchase #3 $226.94   9.413%   $248.3019   $248.30   $248.30   $248.30  
  Purchase #4 $132.86   9.166%   $145.0379   $145.04   $145.05   $145.00  
  Purchase #5 $59.35   8.716%   $64.5229   $64.52   $64.50   $64.50  
  Purchase #6 $238.49   5.593%   $251.8287   $251.83   $251.85   $251.80  
  Purchase #7 $9.61   8.749%   $10.4508   $10.45   $10.45   $10.50  
  7 purchase totals = $805.44       $869.4605   $869.46   $869.45   $869.40