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 $10.46   5.264%   $11.0106   $11.01   $11.00   $11.00  
  Purchase #2 $246.88   8.365%   $267.5315   $267.53   $267.55   $267.50  
  Purchase #3 $204.69   8.828%   $222.76   $222.76   $222.75   $222.80  
  Purchase #4 $199.27   3.137%   $205.5211   $205.52   $205.50   $205.50  
  Purchase #5 $55.84   11.102%   $62.0394   $62.04   $62.05   $62.00  
  Purchase #6 $199.28   13.749%   $226.679   $226.68   $226.70   $226.70  
  Purchase #7 $62.64   9.111%   $68.3471   $68.35   $68.35   $68.30  
  7 purchase totals = $979.06       $1,063.8887   $1,063.89   $1,063.90   $1,063.80