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 $67.75   9.540%   $74.2134   $74.21   $74.20   $74.20  
  Purchase #2 $152.62   5.656%   $161.2522   $161.25   $161.25   $161.30  
  Purchase #3 $59.60   10.474%   $65.8425   $65.84   $65.85   $65.80  
  Purchase #4 $196.52   11.789%   $219.6877   $219.69   $219.70   $219.70  
  Purchase #5 $93.62   10.248%   $103.2142   $103.21   $103.20   $103.20  
  Purchase #6 $243.51   9.754%   $267.262   $267.26   $267.25   $267.30  
  Purchase #7 $217.45   9.426%   $237.9468   $237.95   $237.95   $237.90  
  7 purchase totals = $1,031.07       $1,129.4188   $1,129.41   $1,129.40   $1,129.40