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 $224.52   10.310%   $247.668   $247.67   $247.65   $247.70  
  Purchase #2 $48.80   8.856%   $53.1217   $53.12   $53.10   $53.10  
  Purchase #3 $22.47   9.402%   $24.5826   $24.58   $24.60   $24.60  
  Purchase #4 $6.28   4.735%   $6.5774   $6.58   $6.60   $6.60  
  Purchase #5 $191.93   3.412%   $198.4787   $198.48   $198.50   $198.50  
  Purchase #6 $245.57   9.304%   $268.4178   $268.42   $268.40   $268.40  
  Purchase #7 $204.50   5.627%   $216.0072   $216.01   $216.00   $216.00  
  7 purchase totals = $944.07       $1,014.8534   $1,014.86   $1,014.85   $1,014.90