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 $155.31   9.140%   $169.5053   $169.51   $169.50   $169.50  
  Purchase #2 $67.63   8.710%   $73.5206   $73.52   $73.50   $73.50  
  Purchase #3 $218.76   4.304%   $228.1754   $228.18   $228.20   $228.20  
  Purchase #4 $240.64   7.710%   $259.1933   $259.19   $259.20   $259.20  
  Purchase #5 $83.50   6.133%   $88.6211   $88.62   $88.60   $88.60  
  Purchase #6 $161.84   3.378%   $167.307   $167.31   $167.30   $167.30  
  Purchase #7 $204.92   13.797%   $233.1928   $233.19   $233.20   $233.20  
  7 purchase totals = $1,132.60       $1,219.5155   $1,219.52   $1,219.50   $1,219.50