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	$179.38	11.172%	$199.4203	$199.42	$199.40	$199.40
Purchase #2	$10.70	13.577%	$12.1527	$12.15	$12.15	$12.20
Purchase #3	$74.65	6.837%	$79.7538	$79.75	$79.75	$79.80
Purchase #4	$141.42	7.177%	$151.5697	$151.57	$151.55	$151.60
Purchase #5	$218.41	9.158%	$238.412	$238.41	$238.40	$238.40
Purchase #6	$233.91	6.841%	$249.9118	$249.91	$249.90	$249.90
Purchase #7	$239.31	6.650%	$255.2241	$255.22	$255.20	$255.20
7 purchase totals =	$1,097.78		$1,186.4444	$1,186.43	$1,186.35	$1,186.50