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 $91.28   4.721%   $95.5893   $95.59   $95.60   $95.60  
  Purchase #2 $174.62   8.584%   $189.6094   $189.61   $189.60   $189.60  
  Purchase #3 $168.52   5.489%   $177.7701   $177.77   $177.75   $177.80  
  Purchase #4 $216.54   13.170%   $245.0583   $245.06   $245.05   $245.10  
  Purchase #5 $74.56   3.419%   $77.1092   $77.11   $77.10   $77.10  
  Purchase #6 $40.94   11.723%   $45.7394   $45.74   $45.75   $45.70  
  Purchase #7 $164.98   8.742%   $179.4026   $179.40   $179.40   $179.40  
  7 purchase totals = $931.44       $1,010.2783   $1,010.28   $1,010.25   $1,010.30