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 $245.84   8.819%   $267.5206   $267.52   $267.50   $267.50  
  Purchase #2 $88.51   7.469%   $95.1208   $95.12   $95.10   $95.10  
  Purchase #3 $224.34   8.659%   $243.7656   $243.77   $243.75   $243.80  
  Purchase #4 $50.46   7.164%   $54.075   $54.08   $54.10   $54.10  
  Purchase #5 $238.27   11.527%   $265.7354   $265.74   $265.75   $265.70  
  Purchase #6 $40.65   5.451%   $42.8658   $42.87   $42.85   $42.90  
  Purchase #7 $87.96   5.823%   $93.0819   $93.08   $93.10   $93.10  
  7 purchase totals = $976.03       $1,062.1651   $1,062.18   $1,062.15   $1,062.20