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 $219.40   7.487%   $235.8265   $235.83   $235.85   $235.80  
  Purchase #2 $19.95   4.793%   $20.9062   $20.91   $20.90   $20.90  
  Purchase #3 $211.98   4.288%   $221.0697   $221.07   $221.05   $221.10  
  Purchase #4 $63.93   9.622%   $70.0813   $70.08   $70.10   $70.10  
  Purchase #5 $165.89   13.269%   $187.9019   $187.90   $187.90   $187.90  
  Purchase #6 $50.66   3.826%   $52.5983   $52.60   $52.60   $52.60  
  Purchase #7 $217.89   13.161%   $246.5665   $246.57   $246.55   $246.60  
  7 purchase totals = $949.70       $1,034.9504   $1,034.96   $1,034.95   $1,035.00