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	$149.27	11.573%	$166.545	$166.55	$166.55	$166.50
Purchase #2	$12.81	5.328%	$13.4925	$13.49	$13.50	$13.50
Purchase #3	$55.28	5.700%	$58.431	$58.43	$58.45	$58.40
Purchase #4	$144.63	5.476%	$152.5499	$152.55	$152.55	$152.50
Purchase #5	$111.74	4.113%	$116.3359	$116.34	$116.35	$116.30
Purchase #6	$184.80	3.165%	$190.6489	$190.65	$190.65	$190.60
Purchase #7	$168.32	4.418%	$175.7564	$175.76	$175.75	$175.80
7 purchase totals =	$826.85		$873.7596	$873.77	$873.80	$873.60