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 $68.99   8.671%   $74.9721   $74.97   $74.95   $75.00  
  Purchase #2 $70.50   7.308%   $75.6521   $75.65   $75.65   $75.70  
  Purchase #3 $93.65   4.650%   $98.0047   $98.00   $98.00   $98.00  
  Purchase #4 $224.28   9.269%   $245.0685   $245.07   $245.05   $245.10  
  Purchase #5 $80.30   7.406%   $86.247   $86.25   $86.25   $86.20  
  Purchase #6 $223.50   5.450%   $235.6808   $235.68   $235.70   $235.70  
  Purchase #7 $219.27   5.499%   $231.3277   $231.33   $231.35   $231.30  
  7 purchase totals = $980.49       $1,046.9529   $1,046.95   $1,046.95   $1,047.00