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 $202.96   4.261%   $211.6081   $211.61   $211.60   $211.60  
  Purchase #2 $20.31   8.603%   $22.0573   $22.06   $22.05   $22.10  
  Purchase #3 $55.25   5.440%   $58.2556   $58.26   $58.25   $58.30  
  Purchase #4 $84.35   11.367%   $93.9381   $93.94   $93.95   $93.90  
  Purchase #5 $214.59   8.424%   $232.6671   $232.67   $232.65   $232.70  
  Purchase #6 $95.85   9.302%   $104.766   $104.77   $104.75   $104.80  
  Purchase #7 $202.27   5.200%   $212.788   $212.79   $212.80   $212.80  
  7 purchase totals = $875.58       $936.0802   $936.10   $936.05   $936.20