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 $118.76   3.423%   $122.8252   $122.83   $122.85   $122.80  
  Purchase #2 $189.46   11.575%   $211.39   $211.39   $211.40   $211.40  
  Purchase #3 $232.37   6.280%   $246.9628   $246.96   $246.95   $247.00  
  Purchase #4 $182.79   5.831%   $193.4485   $193.45   $193.45   $193.40  
  Purchase #5 $184.73   13.146%   $209.0146   $209.01   $209.00   $209.00  
  Purchase #6 $54.47   11.457%   $60.7106   $60.71   $60.70   $60.70  
  Purchase #7 $214.48   7.495%   $230.5553   $230.56   $230.55   $230.60  
  7 purchase totals = $1,177.06       $1,274.9070   $1,274.91   $1,274.90   $1,274.90