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	$248.71	11.803%	$278.0652	$278.07	$278.05	$278.10
Purchase #2	$99.98	12.168%	$112.1456	$112.15	$112.15	$112.10
Purchase #3	$131.63	13.449%	$149.3329	$149.33	$149.35	$149.30
Purchase #4	$137.76	12.865%	$155.4828	$155.48	$155.50	$155.50
Purchase #5	$160.90	11.419%	$179.2732	$179.27	$179.25	$179.30
Purchase #6	$40.33	13.309%	$45.6975	$45.70	$45.70	$45.70
Purchase #7	$129.76	10.439%	$143.3056	$143.31	$143.30	$143.30
7 purchase totals =	$949.07		$1,063.3028	$1,063.31	$1,063.30	$1,063.30