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 $33.80   5.362%   $35.6124   $35.61   $35.60   $35.60  
  Purchase #2 $222.99   9.319%   $243.7704   $243.77   $243.75   $243.80  
  Purchase #3 $48.33   7.820%   $52.1094   $52.11   $52.10   $52.10  
  Purchase #4 $175.36   6.295%   $186.3989   $186.40   $186.40   $186.40  
  Purchase #5 $98.29   12.669%   $110.7424   $110.74   $110.75   $110.70  
  Purchase #6 $57.75   7.289%   $61.9594   $61.96   $61.95   $62.00  
  Purchase #7 $40.52   3.279%   $41.8487   $41.85   $41.85   $41.80  
  7 purchase totals = $677.04       $732.4416   $732.44   $732.40   $732.40