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 $84.60   9.677%   $92.7867   $92.79   $92.80   $92.80  
  Purchase #2 $213.27   8.453%   $231.2977   $231.30   $231.30   $231.30  
  Purchase #3 $103.33   4.797%   $108.2867   $108.29   $108.30   $108.30  
  Purchase #4 $233.94   5.262%   $246.2499   $246.25   $246.25   $246.20  
  Purchase #5 $179.62   5.846%   $190.1206   $190.12   $190.10   $190.10  
  Purchase #6 $31.42   11.418%   $35.0075   $35.01   $35.00   $35.00  
  Purchase #7 $195.69   8.687%   $212.6896   $212.69   $212.70   $212.70  
  7 purchase totals = $1,041.87       $1,116.4387   $1,116.45   $1,116.45   $1,116.40