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 $85.75   10.511%   $94.7632   $94.76   $94.75   $94.80  
  Purchase #2 $144.89   12.167%   $162.5188   $162.52   $162.50   $162.50  
  Purchase #3 $166.47   9.105%   $181.6271   $181.63   $181.65   $181.60  
  Purchase #4 $144.66   3.599%   $149.8663   $149.87   $149.85   $149.90  
  Purchase #5 $179.84   8.317%   $194.7973   $194.80   $194.80   $194.80  
  Purchase #6 $42.82   8.705%   $46.5475   $46.55   $46.55   $46.50  
  Purchase #7 $190.40   6.624%   $203.0121   $203.01   $203.00   $203.00  
  7 purchase totals = $954.83       $1,033.1323   $1,033.14   $1,033.10   $1,033.10