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 $44.47   8.528%   $48.2624   $48.26   $48.25   $48.30  
  Purchase #2 $159.97   4.126%   $166.5704   $166.57   $166.55   $166.60  
  Purchase #3 $68.66   12.487%   $77.2336   $77.23   $77.25   $77.20  
  Purchase #4 $246.50   9.608%   $270.1837   $270.18   $270.20   $270.20  
  Purchase #5 $231.83   9.247%   $253.2673   $253.27   $253.25   $253.30  
  Purchase #6 $176.30   3.802%   $183.0029   $183.00   $183.00   $183.00  
  Purchase #7 $156.93   7.823%   $169.2066   $169.21   $169.20   $169.20  
  7 purchase totals = $1,084.66       $1,167.7269   $1,167.72   $1,167.70   $1,167.80