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	$228.65	13.501%	$259.52	$259.52	$259.50	$259.50
Purchase #2	$152.41	3.643%	$157.9623	$157.96	$157.95	$158.00
Purchase #3	$46.78	7.839%	$50.4471	$50.45	$50.45	$50.40
Purchase #4	$53.61	11.661%	$59.8615	$59.86	$59.85	$59.90
Purchase #5	$161.87	7.694%	$174.3243	$174.32	$174.30	$174.30
Purchase #6	$164.81	4.715%	$172.5808	$172.58	$172.60	$172.60
Purchase #7	$198.50	5.793%	$209.9991	$210.00	$210.00	$210.00
7 purchase totals =	$1,006.63		$1,084.6951	$1,084.69	$1,084.65	$1,084.70