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 $13.72   7.511%   $14.7505   $14.75   $14.75   $14.80  
  Purchase #2 $156.64   11.740%   $175.0295   $175.03   $175.05   $175.00  
  Purchase #3 $217.57   10.719%   $240.8913   $240.89   $240.90   $240.90  
  Purchase #4 $157.84   12.654%   $177.8131   $177.81   $177.80   $177.80  
  Purchase #5 $110.97   12.251%   $124.5649   $124.56   $124.55   $124.60  
  Purchase #6 $244.68   10.367%   $270.046   $270.05   $270.05   $270.00  
  Purchase #7 $194.91   3.261%   $201.266   $201.27   $201.25   $201.30  
  7 purchase totals = $1,096.33       $1,204.3613   $1,204.36   $1,204.35   $1,204.40