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 $195.43   7.180%   $209.4619   $209.46   $209.45   $209.50  
  Purchase #2 $230.60   6.663%   $245.9649   $245.96   $245.95   $246.00  
  Purchase #3 $43.72   4.671%   $45.7622   $45.76   $45.75   $45.80  
  Purchase #4 $114.50   6.186%   $121.583   $121.58   $121.60   $121.60  
  Purchase #5 $189.74   12.352%   $213.1767   $213.18   $213.20   $213.20  
  Purchase #6 $216.40   5.327%   $227.9276   $227.93   $227.95   $227.90  
  Purchase #7 $56.93   11.280%   $63.3517   $63.35   $63.35   $63.40  
  7 purchase totals = $1,047.32       $1,127.2280   $1,127.22   $1,127.25   $1,127.40