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 $187.38   7.772%   $201.9432   $201.94   $201.95   $201.90  
  Purchase #2 $23.98   7.642%   $25.8126   $25.81   $25.80   $25.80  
  Purchase #3 $58.81   5.142%   $61.834   $61.83   $61.85   $61.80  
  Purchase #4 $85.52   13.670%   $97.2106   $97.21   $97.20   $97.20  
  Purchase #5 $204.87   8.523%   $222.3311   $222.33   $222.35   $222.30  
  Purchase #6 $82.90   6.386%   $88.194   $88.19   $88.20   $88.20  
  Purchase #7 $50.38   11.722%   $56.2855   $56.29   $56.30   $56.30  
  7 purchase totals = $693.84       $753.6110   $753.60   $753.65   $753.50