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 $202.52   11.607%   $226.0265   $226.03   $226.05   $226.00  
  Purchase #2 $96.35   12.294%   $108.1953   $108.20   $108.20   $108.20  
  Purchase #3 $63.57   3.434%   $65.753   $65.75   $65.75   $65.80  
  Purchase #4 $42.67   9.330%   $46.6511   $46.65   $46.65   $46.70  
  Purchase #5 $156.31   3.236%   $161.3682   $161.37   $161.35   $161.40  
  Purchase #6 $94.44   13.767%   $107.4416   $107.44   $107.45   $107.40  
  Purchase #7 $221.50   13.765%   $251.9895   $251.99   $252.00   $252.00  
  7 purchase totals = $877.36       $967.4252   $967.43   $967.45   $967.50