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 $183.96   9.451%   $201.3461   $201.35   $201.35   $201.30  
  Purchase #2 $43.89   10.697%   $48.5849   $48.58   $48.60   $48.60  
  Purchase #3 $53.25   10.415%   $58.796   $58.80   $58.80   $58.80  
  Purchase #4 $219.81   5.633%   $232.1919   $232.19   $232.20   $232.20  
  Purchase #5 $250.50   6.663%   $267.1908   $267.19   $267.20   $267.20  
  Purchase #6 $212.31   8.809%   $231.0124   $231.01   $231.00   $231.00  
  Purchase #7 $243.88   12.434%   $274.204   $274.20   $274.20   $274.20  
  7 purchase totals = $1,207.60       $1,313.3261   $1,313.32   $1,313.35   $1,313.30