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 $68.75   5.644%   $72.6303   $72.63   $72.65   $72.60  
  Purchase #2 $41.57   3.801%   $43.1501   $43.15   $43.15   $43.20  
  Purchase #3 $143.75   4.685%   $150.4847   $150.48   $150.50   $150.50  
  Purchase #4 $189.43   3.258%   $195.6016   $195.60   $195.60   $195.60  
  Purchase #5 $18.35   8.281%   $19.8696   $19.87   $19.85   $19.90  
  Purchase #6 $169.72   6.674%   $181.0471   $181.05   $181.05   $181.00  
  Purchase #7 $221.44   5.103%   $232.7401   $232.74   $232.75   $232.70  
  7 purchase totals = $853.01       $895.5235   $895.52   $895.55   $895.50