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 $168.31   11.515%   $187.6909   $187.69   $187.70   $187.70  
  Purchase #2 $32.95   10.344%   $36.3583   $36.36   $36.35   $36.40  
  Purchase #3 $125.98   8.633%   $136.8559   $136.86   $136.85   $136.90  
  Purchase #4 $244.52   8.858%   $266.1796   $266.18   $266.20   $266.20  
  Purchase #5 $204.45   8.720%   $222.278   $222.28   $222.30   $222.30  
  Purchase #6 $96.89   6.319%   $103.0125   $103.01   $103.00   $103.00  
  Purchase #7 $208.58   11.145%   $231.8262   $231.83   $231.85   $231.80  
  7 purchase totals = $1,081.68       $1,184.2014   $1,184.21   $1,184.25   $1,184.30