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	$183.52	6.521%	$195.4873	$195.49	$195.50	$195.50
Purchase #2	$141.44	7.804%	$152.478	$152.48	$152.50	$152.50
Purchase #3	$53.92	5.709%	$56.9983	$57.00	$57.00	$57.00
Purchase #4	$134.35	12.551%	$151.2123	$151.21	$151.20	$151.20
Purchase #5	$182.89	12.180%	$205.166	$205.17	$205.15	$205.20
Purchase #6	$168.72	4.231%	$175.8585	$175.86	$175.85	$175.90
Purchase #7	$29.55	6.374%	$31.4335	$31.43	$31.45	$31.40
7 purchase totals =	$894.39		$968.6339	$968.64	$968.65	$968.70