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 $69.62   4.443%   $72.7132   $72.71   $72.70   $72.70  
  Purchase #2 $187.57   12.474%   $210.9675   $210.97   $210.95   $211.00  
  Purchase #3 $211.84   10.735%   $234.581   $234.58   $234.60   $234.60  
  Purchase #4 $98.60   9.871%   $108.3328   $108.33   $108.35   $108.30  
  Purchase #5 $89.40   5.456%   $94.2777   $94.28   $94.30   $94.30  
  Purchase #6 $225.34   11.825%   $251.9865   $251.99   $252.00   $252.00  
  Purchase #7 $195.38   3.121%   $201.4778   $201.48   $201.50   $201.50  
  7 purchase totals = $1,077.75       $1,174.3365   $1,174.34   $1,174.40   $1,174.40