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 $161.83   8.300%   $175.2619   $175.26   $175.25   $175.30  
  Purchase #2 $157.68   7.620%   $169.6952   $169.70   $169.70   $169.70  
  Purchase #3 $24.35   4.420%   $25.4263   $25.43   $25.45   $25.40  
  Purchase #4 $193.33   9.146%   $211.012   $211.01   $211.00   $211.00  
  Purchase #5 $119.53   5.565%   $126.1818   $126.18   $126.20   $126.20  
  Purchase #6 $43.65   4.278%   $45.5173   $45.52   $45.50   $45.50  
  Purchase #7 $224.30   7.246%   $240.5528   $240.55   $240.55   $240.60  
  7 purchase totals = $924.67       $993.6473   $993.65   $993.65   $993.70