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	$111.93	12.353%	$125.7567	$125.76	$125.75	$125.80
Purchase #2	$195.80	6.786%	$209.087	$209.09	$209.10	$209.10
Purchase #3	$28.93	13.738%	$32.9044	$32.90	$32.90	$32.90
Purchase #4	$40.25	5.733%	$42.5575	$42.56	$42.55	$42.60
Purchase #5	$16.52	10.636%	$18.2771	$18.28	$18.30	$18.30
Purchase #6	$147.94	13.109%	$167.3335	$167.33	$167.35	$167.30
Purchase #7	$56.85	3.161%	$58.647	$58.65	$58.65	$58.60
7 purchase totals =	$598.22		$654.5632	$654.57	$654.60	$654.60