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 $58.37   7.591%   $62.8009   $62.80   $62.80   $62.80  
  Purchase #2 $218.31   9.214%   $238.4251   $238.43   $238.45   $238.40  
  Purchase #3 $196.92   6.246%   $209.2196   $209.22   $209.20   $209.20  
  Purchase #4 $193.50   3.570%   $200.408   $200.41   $200.40   $200.40  
  Purchase #5 $201.80   4.623%   $211.1292   $211.13   $211.15   $211.10  
  Purchase #6 $120.82   3.679%   $125.265   $125.27   $125.25   $125.30  
  Purchase #7 $210.67   5.365%   $221.9724   $221.97   $221.95   $222.00  
  7 purchase totals = $1,200.39       $1,269.2202   $1,269.23   $1,269.20   $1,269.20