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 $96.33   9.250%   $105.2405   $105.24   $105.25   $105.20  
  Purchase #2 $59.96   13.405%   $67.9976   $68.00   $68.00   $68.00  
  Purchase #3 $132.93   6.679%   $141.8084   $141.81   $141.80   $141.80  
  Purchase #4 $244.30   12.785%   $275.5338   $275.53   $275.55   $275.50  
  Purchase #5 $187.44   11.518%   $209.0293   $209.03   $209.05   $209.00  
  Purchase #6 $119.72   12.415%   $134.5832   $134.58   $134.60   $134.60  
  Purchase #7 $77.58   3.751%   $80.49   $80.49   $80.50   $80.50  
  7 purchase totals = $918.26       $1,014.6828   $1,014.68   $1,014.75   $1,014.60