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	$142.66	7.639%	$153.5578	$153.56	$153.55	$153.60
Purchase #2	$71.87	9.786%	$78.9032	$78.90	$78.90	$78.90
Purchase #3	$178.55	5.439%	$188.2613	$188.26	$188.25	$188.30
Purchase #4	$70.30	11.236%	$78.1989	$78.20	$78.20	$78.20
Purchase #5	$148.76	5.338%	$156.7008	$156.70	$156.70	$156.70
Purchase #6	$66.72	6.739%	$71.2163	$71.22	$71.20	$71.20
Purchase #7	$197.57	4.443%	$206.348	$206.35	$206.35	$206.30
7 purchase totals =	$876.43		$933.1863	$933.19	$933.15	$933.20