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 $44.67   7.517%   $48.0278   $48.03   $48.05   $48.00  
  Purchase #2 $166.98   11.849%   $186.7655   $186.77   $186.75   $186.80  
  Purchase #3 $121.58   8.302%   $131.6736   $131.67   $131.65   $131.70  
  Purchase #4 $163.35   10.797%   $180.9869   $180.99   $181.00   $181.00  
  Purchase #5 $161.52   12.364%   $181.4903   $181.49   $181.50   $181.50  
  Purchase #6 $31.86   9.516%   $34.8918   $34.89   $34.90   $34.90  
  Purchase #7 $175.51   5.476%   $185.1209   $185.12   $185.10   $185.10  
  7 purchase totals = $865.47       $948.9568   $948.96   $948.95   $949.00