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	$72.41	9.634%	$79.386	$79.39	$79.40	$79.40
Purchase #2	$111.76	13.641%	$127.0052	$127.01	$127.00	$127.00
Purchase #3	$173.62	7.355%	$186.3898	$186.39	$186.40	$186.40
Purchase #4	$247.94	10.540%	$274.0729	$274.07	$274.05	$274.10
Purchase #5	$46.84	9.364%	$51.2261	$51.23	$51.25	$51.20
Purchase #6	$195.55	11.567%	$218.1693	$218.17	$218.15	$218.20
Purchase #7	$59.47	11.630%	$66.3864	$66.39	$66.40	$66.40
7 purchase totals =	$907.59		$1,002.6357	$1,002.65	$1,002.65	$1,002.70