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 $72.28   5.602%   $76.3291   $76.33   $76.35   $76.30  
  Purchase #2 $211.72   9.739%   $232.3394   $232.34   $232.35   $232.30  
  Purchase #3 $165.65   7.163%   $177.5155   $177.52   $177.50   $177.50  
  Purchase #4 $236.74   4.138%   $246.5363   $246.54   $246.55   $246.50  
  Purchase #5 $201.87   9.333%   $220.7105   $220.71   $220.70   $220.70  
  Purchase #6 $191.35   7.308%   $205.3339   $205.33   $205.35   $205.30  
  Purchase #7 $70.64   7.650%   $76.044   $76.04   $76.05   $76.00  
  7 purchase totals = $1,150.25       $1,234.8087   $1,234.81   $1,234.85   $1,234.60