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 $32.50   7.283%   $34.867   $34.87   $34.85   $34.90  
  Purchase #2 $181.93   11.519%   $202.8865   $202.89   $202.90   $202.90  
  Purchase #3 $62.58   9.351%   $68.4319   $68.43   $68.45   $68.40  
  Purchase #4 $196.36   6.542%   $209.2059   $209.21   $209.20   $209.20  
  Purchase #5 $53.58   8.329%   $58.0427   $58.04   $58.05   $58.00  
  Purchase #6 $165.55   6.324%   $176.0194   $176.02   $176.00   $176.00  
  Purchase #7 $190.74   6.448%   $203.0389   $203.04   $203.05   $203.00  
  7 purchase totals = $883.24       $952.4923   $952.50   $952.50   $952.40