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 $126.48   6.186%   $134.3041   $134.30   $134.30   $134.30  
  Purchase #2 $195.43   10.527%   $216.0029   $216.00   $216.00   $216.00  
  Purchase #3 $242.39   13.283%   $274.5867   $274.59   $274.60   $274.60  
  Purchase #4 $197.87   7.250%   $212.2156   $212.22   $212.20   $212.20  
  Purchase #5 $46.76   13.764%   $53.196   $53.20   $53.20   $53.20  
  Purchase #6 $174.62   3.241%   $180.2794   $180.28   $180.30   $180.30  
  Purchase #7 $62.29   5.695%   $65.8374   $65.84   $65.85   $65.80  
  7 purchase totals = $1,045.84       $1,136.4221   $1,136.43   $1,136.45   $1,136.40