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 $173.81   11.740%   $194.2153   $194.22   $194.20   $194.20  
  Purchase #2 $150.38   8.850%   $163.6886   $163.69   $163.70   $163.70  
  Purchase #3 $118.90   10.700%   $131.6223   $131.62   $131.60   $131.60  
  Purchase #4 $209.91   10.442%   $231.8288   $231.83   $231.85   $231.80  
  Purchase #5 $219.81   10.249%   $242.3383   $242.34   $242.35   $242.30  
  Purchase #6 $226.52   8.791%   $246.4334   $246.43   $246.45   $246.40  
  Purchase #7 $49.38   4.685%   $51.6935   $51.69   $51.70   $51.70  
  7 purchase totals = $1,148.71       $1,261.8202   $1,261.82   $1,261.85   $1,261.70