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	$121.52	5.171%	$127.8038	$127.80	$127.80	$127.80
Purchase #2	$40.44	12.446%	$45.4732	$45.47	$45.45	$45.50
Purchase #3	$61.96	3.451%	$64.0982	$64.10	$64.10	$64.10
Purchase #4	$250.37	3.195%	$258.3693	$258.37	$258.35	$258.40
Purchase #5	$217.47	4.155%	$226.5059	$226.51	$226.50	$226.50
Purchase #6	$143.48	11.741%	$160.326	$160.33	$160.35	$160.30
Purchase #7	$59.72	3.675%	$61.9147	$61.91	$61.90	$61.90
7 purchase totals =	$894.96		$944.4911	$944.49	$944.45	$944.50