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 $93.32   3.679%   $96.7532   $96.75   $96.75   $96.80  
  Purchase #2 $160.96   8.499%   $174.64   $174.64   $174.65   $174.60  
  Purchase #3 $215.97   3.563%   $223.665   $223.67   $223.65   $223.70  
  Purchase #4 $33.77   6.550%   $35.9819   $35.98   $36.00   $36.00  
  Purchase #5 $245.42   7.528%   $263.8952   $263.90   $263.90   $263.90  
  Purchase #6 $196.79   7.310%   $211.1753   $211.18   $211.20   $211.20  
  Purchase #7 $88.40   8.427%   $95.8495   $95.85   $95.85   $95.80  
  7 purchase totals = $1,034.63       $1,101.9601   $1,101.97   $1,102.00   $1,102.00