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 $57.40   7.842%   $61.9013   $61.90   $61.90   $61.90  
  Purchase #2 $219.86   7.156%   $235.5932   $235.59   $235.60   $235.60  
  Purchase #3 $229.44   4.412%   $239.5629   $239.56   $239.55   $239.60  
  Purchase #4 $213.73   5.179%   $224.7991   $224.80   $224.80   $224.80  
  Purchase #5 $26.35   3.525%   $27.2788   $27.28   $27.30   $27.30  
  Purchase #6 $111.84   7.466%   $120.19   $120.19   $120.20   $120.20  
  Purchase #7 $15.49   5.245%   $16.3025   $16.30   $16.30   $16.30  
  7 purchase totals = $874.11       $925.6278   $925.62   $925.65   $925.70