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	$142.33	7.369%	$152.8183	$152.82	$152.80	$152.80
Purchase #2	$60.61	10.802%	$67.1571	$67.16	$67.15	$67.20
Purchase #3	$110.44	5.624%	$116.6511	$116.65	$116.65	$116.70
Purchase #4	$66.72	3.220%	$68.8684	$68.87	$68.85	$68.90
Purchase #5	$243.81	4.353%	$254.423	$254.42	$254.40	$254.40
Purchase #6	$86.94	6.466%	$92.5615	$92.56	$92.55	$92.60
Purchase #7	$190.82	13.866%	$217.2791	$217.28	$217.30	$217.30
7 purchase totals =	$901.67		$969.7585	$969.76	$969.70	$969.90