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	$240.38	3.333%	$248.3919	$248.39	$248.40	$248.40
Purchase #2	$93.54	7.226%	$100.2992	$100.30	$100.30	$100.30
Purchase #3	$217.53	6.257%	$231.1409	$231.14	$231.15	$231.10
Purchase #4	$222.65	3.419%	$230.2624	$230.26	$230.25	$230.30
Purchase #5	$196.33	12.771%	$221.4033	$221.40	$221.40	$221.40
Purchase #6	$58.82	6.443%	$62.6098	$62.61	$62.60	$62.60
Purchase #7	$114.79	13.729%	$130.5495	$130.55	$130.55	$130.50
7 purchase totals =	$1,144.04		$1,224.6570	$1,224.65	$1,224.65	$1,224.60