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 $188.74   9.682%   $207.0138   $207.01   $207.00   $207.00  
  Purchase #2 $201.95   3.769%   $209.5615   $209.56   $209.55   $209.60  
  Purchase #3 $26.38   12.354%   $29.639   $29.64   $29.65   $29.60  
  Purchase #4 $150.69   10.809%   $166.9781   $166.98   $167.00   $167.00  
  Purchase #5 $193.84   4.209%   $201.9987   $202.00   $202.00   $202.00  
  Purchase #6 $191.89   6.532%   $204.4243   $204.42   $204.40   $204.40  
  Purchase #7 $150.59   10.386%   $166.2303   $166.23   $166.25   $166.20  
  7 purchase totals = $1,104.08       $1,185.8457   $1,185.84   $1,185.85   $1,185.80