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 $191.85   8.265%   $207.7064   $207.71   $207.70   $207.70  
  Purchase #2 $211.45   5.511%   $223.103   $223.10   $223.10   $223.10  
  Purchase #3 $56.89   8.620%   $61.7939   $61.79   $61.80   $61.80  
  Purchase #4 $158.42   13.309%   $179.5041   $179.50   $179.50   $179.50  
  Purchase #5 $34.77   3.430%   $35.9626   $35.96   $35.95   $36.00  
  Purchase #6 $141.84   5.835%   $150.1164   $150.12   $150.10   $150.10  
  Purchase #7 $162.78   8.365%   $176.3965   $176.40   $176.40   $176.40  
  7 purchase totals = $958.00       $1,034.5829   $1,034.58   $1,034.55   $1,034.60