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 $34.26   8.802%   $37.2756   $37.28   $37.30   $37.30  
  Purchase #2 $95.88   12.874%   $108.2236   $108.22   $108.20   $108.20  
  Purchase #3 $52.29   4.692%   $54.7434   $54.74   $54.75   $54.70  
  Purchase #4 $205.51   5.869%   $217.5714   $217.57   $217.55   $217.60  
  Purchase #5 $197.32   4.502%   $206.2033   $206.20   $206.20   $206.20  
  Purchase #6 $238.95   5.586%   $252.2977   $252.30   $252.30   $252.30  
  Purchase #7 $217.98   3.547%   $225.7118   $225.71   $225.70   $225.70  
  7 purchase totals = $1,042.19       $1,102.0268   $1,102.02   $1,102.00   $1,102.00