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 $194.95   4.352%   $203.4342   $203.43   $203.45   $203.40  
  Purchase #2 $59.39   9.545%   $65.0588   $65.06   $65.05   $65.10  
  Purchase #3 $179.90   6.596%   $191.7662   $191.77   $191.75   $191.80  
  Purchase #4 $70.33   6.180%   $74.6764   $74.68   $74.70   $74.70  
  Purchase #5 $91.67   10.654%   $101.4365   $101.44   $101.45   $101.40  
  Purchase #6 $201.77   6.412%   $214.7075   $214.71   $214.70   $214.70  
  Purchase #7 $246.41   11.226%   $274.072   $274.07   $274.05   $274.10  
  7 purchase totals = $1,044.42       $1,125.1516   $1,125.16   $1,125.15   $1,125.20