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	$176.57	12.223%	$198.1522	$198.15	$198.15	$198.20
Purchase #2	$236.90	8.279%	$256.513	$256.51	$256.50	$256.50
Purchase #3	$101.49	5.295%	$106.8639	$106.86	$106.85	$106.90
Purchase #4	$78.51	5.104%	$82.5172	$82.52	$82.50	$82.50
Purchase #5	$11.59	6.815%	$12.3799	$12.38	$12.40	$12.40
Purchase #6	$46.53	3.389%	$48.1069	$48.11	$48.10	$48.10
Purchase #7	$193.54	6.320%	$205.7717	$205.77	$205.75	$205.80
7 purchase totals =	$845.13		$910.3048	$910.30	$910.25	$910.40