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 $166.85   5.333%   $175.7481   $175.75   $175.75   $175.70  
  Purchase #2 $246.78   8.280%   $267.2134   $267.21   $267.20   $267.20  
  Purchase #3 $173.36   8.697%   $188.4371   $188.44   $188.45   $188.40  
  Purchase #4 $31.41   6.427%   $33.4287   $33.43   $33.45   $33.40  
  Purchase #5 $208.81   3.282%   $215.6631   $215.66   $215.65   $215.70  
  Purchase #6 $65.40   6.762%   $69.8223   $69.82   $69.80   $69.80  
  Purchase #7 $100.35   13.261%   $113.6574   $113.66   $113.65   $113.70  
  7 purchase totals = $992.96       $1,063.9701   $1,063.97   $1,063.95   $1,063.90