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	$173.28	12.325%	$194.6368	$194.64	$194.65	$194.60
Purchase #2	$178.92	5.261%	$188.333	$188.33	$188.35	$188.30
Purchase #3	$135.88	12.403%	$152.7332	$152.73	$152.75	$152.70
Purchase #4	$32.27	4.227%	$33.6341	$33.63	$33.65	$33.60
Purchase #5	$179.83	8.211%	$194.5958	$194.60	$194.60	$194.60
Purchase #6	$77.56	11.604%	$86.5601	$86.56	$86.55	$86.60
Purchase #7	$74.98	4.843%	$78.6113	$78.61	$78.60	$78.60
7 purchase totals =	$852.72		$929.1043	$929.10	$929.15	$929.00