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	$74.42	3.788%	$77.239	$77.24	$77.25	$77.20
Purchase #2	$100.77	3.633%	$104.431	$104.43	$104.45	$104.40
Purchase #3	$156.98	5.657%	$165.8604	$165.86	$165.85	$165.90
Purchase #4	$237.28	13.844%	$270.129	$270.13	$270.15	$270.10
Purchase #5	$221.72	8.420%	$240.3888	$240.39	$240.40	$240.40
Purchase #6	$64.95	4.623%	$67.9526	$67.95	$67.95	$68.00
Purchase #7	$105.74	5.401%	$111.451	$111.45	$111.45	$111.50
7 purchase totals =	$961.86		$1,037.4518	$1,037.45	$1,037.50	$1,037.50