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	$217.61	5.730%	$230.0791	$230.08	$230.10	$230.10
Purchase #2	$116.55	11.269%	$129.684	$129.68	$129.70	$129.70
Purchase #3	$154.25	13.142%	$174.5215	$174.52	$174.50	$174.50
Purchase #4	$183.42	12.167%	$205.7367	$205.74	$205.75	$205.70
Purchase #5	$59.73	3.221%	$61.6539	$61.65	$61.65	$61.70
Purchase #6	$64.42	10.132%	$70.947	$70.95	$70.95	$70.90
Purchase #7	$118.39	10.772%	$131.143	$131.14	$131.15	$131.10
7 purchase totals =	$914.37		$1,003.7652	$1,003.76	$1,003.80	$1,003.70