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	$14.81	7.482%	$15.9181	$15.92	$15.90	$15.90
Purchase #2	$168.50	11.240%	$187.4394	$187.44	$187.45	$187.40
Purchase #3	$186.31	5.423%	$196.4136	$196.41	$196.40	$196.40
Purchase #4	$18.91	4.218%	$19.7076	$19.71	$19.70	$19.70
Purchase #5	$40.90	10.815%	$45.3233	$45.32	$45.30	$45.30
Purchase #6	$244.66	8.231%	$264.798	$264.80	$264.80	$264.80
Purchase #7	$155.51	9.219%	$169.8465	$169.85	$169.85	$169.80
7 purchase totals =	$829.60		$899.4465	$899.45	$899.40	$899.30