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 $85.93   7.803%   $92.6351   $92.64   $92.65   $92.60  
  Purchase #2 $172.74   5.234%   $181.7812   $181.78   $181.80   $181.80  
  Purchase #3 $85.96   11.767%   $96.0749   $96.07   $96.05   $96.10  
  Purchase #4 $209.50   12.564%   $235.8216   $235.82   $235.80   $235.80  
  Purchase #5 $127.45   9.521%   $139.5845   $139.58   $139.60   $139.60  
  Purchase #6 $145.76   5.392%   $153.6194   $153.62   $153.60   $153.60  
  Purchase #7 $235.92   3.503%   $244.1843   $244.18   $244.20   $244.20  
  7 purchase totals = $1,063.26       $1,143.7010   $1,143.69   $1,143.70   $1,143.70