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	$39.78	9.562%	$43.5838	$43.58	$43.60	$43.60
Purchase #2	$238.58	10.830%	$264.4182	$264.42	$264.40	$264.40
Purchase #3	$45.83	3.858%	$47.5981	$47.60	$47.60	$47.60
Purchase #4	$112.73	13.262%	$127.6803	$127.68	$127.70	$127.70
Purchase #5	$248.70	10.201%	$274.0699	$274.07	$274.05	$274.10
Purchase #6	$240.90	9.117%	$262.8629	$262.86	$262.85	$262.90
Purchase #7	$130.27	7.315%	$139.7993	$139.80	$139.80	$139.80
7 purchase totals =	$1,056.79		$1,160.0125	$1,160.01	$1,160.00	$1,160.10