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 $117.52   7.465%   $126.2929   $126.29   $126.30   $126.30  
  Purchase #2 $67.89   7.224%   $72.7944   $72.79   $72.80   $72.80  
  Purchase #3 $79.93   6.574%   $85.1846   $85.18   $85.20   $85.20  
  Purchase #4 $228.32   4.244%   $238.0099   $238.01   $238.00   $238.00  
  Purchase #5 $81.95   13.557%   $93.06   $93.06   $93.05   $93.10  
  Purchase #6 $232.43   7.853%   $250.6827   $250.68   $250.70   $250.70  
  Purchase #7 $123.98   4.137%   $129.1091   $129.11   $129.10   $129.10  
  7 purchase totals = $932.02       $995.1336   $995.12   $995.15   $995.20