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 $69.30   10.412%   $76.5155   $76.52   $76.50   $76.50  
  Purchase #2 $46.60   4.791%   $48.8326   $48.83   $48.85   $48.80  
  Purchase #3 $231.93   5.623%   $244.9714   $244.97   $244.95   $245.00  
  Purchase #4 $229.46   9.552%   $251.378   $251.38   $251.40   $251.40  
  Purchase #5 $181.56   11.320%   $202.1126   $202.11   $202.10   $202.10  
  Purchase #6 $48.39   4.740%   $50.6837   $50.68   $50.70   $50.70  
  Purchase #7 $11.71   5.304%   $12.3311   $12.33   $12.35   $12.30  
  7 purchase totals = $818.95       $886.8249   $886.82   $886.85   $886.80