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 $43.58   3.151%   $44.9532   $44.95   $44.95   $45.00  
  Purchase #2 $164.82   9.114%   $179.8417   $179.84   $179.85   $179.80  
  Purchase #3 $232.25   5.713%   $245.5184   $245.52   $245.50   $245.50  
  Purchase #4 $61.64   11.397%   $68.6651   $68.67   $68.65   $68.70  
  Purchase #5 $90.30   6.439%   $96.1144   $96.11   $96.10   $96.10  
  Purchase #6 $241.71   11.824%   $270.2898   $270.29   $270.30   $270.30  
  Purchase #7 $28.26   4.500%   $29.5317   $29.53   $29.55   $29.50  
  7 purchase totals = $862.56       $934.9143   $934.91   $934.90   $934.90