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	$118.27	11.465%	$131.8297	$131.83	$131.85	$131.80
Purchase #2	$248.52	4.374%	$259.3903	$259.39	$259.40	$259.40
Purchase #3	$88.63	7.354%	$95.1479	$95.15	$95.15	$95.10
Purchase #4	$219.48	7.176%	$235.2299	$235.23	$235.25	$235.20
Purchase #5	$71.76	3.850%	$74.5228	$74.52	$74.50	$74.50
Purchase #6	$217.89	12.752%	$245.6753	$245.68	$245.70	$245.70
Purchase #7	$40.70	13.160%	$46.0561	$46.06	$46.05	$46.10
7 purchase totals =	$1,005.25		$1,087.8520	$1,087.86	$1,087.90	$1,087.80