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 $88.61   8.555%   $96.1906   $96.19   $96.20   $96.20  
  Purchase #2 $167.29   4.688%   $175.1326   $175.13   $175.15   $175.10  
  Purchase #3 $199.88   5.103%   $210.0799   $210.08   $210.10   $210.10  
  Purchase #4 $223.70   10.831%   $247.9289   $247.93   $247.95   $247.90  
  Purchase #5 $204.48   9.300%   $223.4966   $223.50   $223.50   $223.50  
  Purchase #6 $174.43   7.821%   $188.0722   $188.07   $188.05   $188.10  
  Purchase #7 $56.94   8.504%   $61.7822   $61.78   $61.80   $61.80  
  7 purchase totals = $1,115.33       $1,202.6830   $1,202.68   $1,202.75   $1,202.70