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 $223.77   4.855%   $234.634   $234.63   $234.65   $234.60  
  Purchase #2 $181.70   11.153%   $201.965   $201.97   $201.95   $202.00  
  Purchase #3 $93.78   7.245%   $100.5744   $100.57   $100.55   $100.60  
  Purchase #4 $246.32   6.383%   $262.0426   $262.04   $262.05   $262.00  
  Purchase #5 $97.83   4.731%   $102.4583   $102.46   $102.45   $102.50  
  Purchase #6 $59.28   13.279%   $67.1518   $67.15   $67.15   $67.20  
  Purchase #7 $60.44   9.352%   $66.0923   $66.09   $66.10   $66.10  
  7 purchase totals = $963.12       $1,034.9184   $1,034.91   $1,034.90   $1,035.00