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	$42.28	7.867%	$45.6062	$45.61	$45.60	$45.60
Purchase #2	$41.35	9.190%	$45.1501	$45.15	$45.15	$45.20
Purchase #3	$227.65	5.728%	$240.6898	$240.69	$240.70	$240.70
Purchase #4	$188.68	13.705%	$214.5386	$214.54	$214.55	$214.50
Purchase #5	$27.98	3.135%	$28.8572	$28.86	$28.85	$28.90
Purchase #6	$212.50	3.126%	$219.1428	$219.14	$219.15	$219.10
Purchase #7	$204.38	7.528%	$219.7657	$219.77	$219.75	$219.80
7 purchase totals =	$944.82		$1,013.7504	$1,013.76	$1,013.75	$1,013.80