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	$32.49	11.141%	$36.1097	$36.11	$36.10	$36.10
Purchase #2	$249.80	11.222%	$277.8326	$277.83	$277.85	$277.80
Purchase #3	$160.49	13.785%	$182.6135	$182.61	$182.60	$182.60
Purchase #4	$91.45	8.607%	$99.3211	$99.32	$99.30	$99.30
Purchase #5	$185.30	11.407%	$206.4372	$206.44	$206.45	$206.40
Purchase #6	$49.41	9.861%	$54.2823	$54.28	$54.30	$54.30
Purchase #7	$249.78	10.115%	$275.0452	$275.05	$275.05	$275.00
7 purchase totals =	$1,018.72		$1,131.6416	$1,131.64	$1,131.65	$1,131.50