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	$214.70	6.167%	$227.9405	$227.94	$227.95	$227.90
Purchase #2	$194.66	12.800%	$219.5765	$219.58	$219.60	$219.60
Purchase #3	$106.34	9.770%	$116.7294	$116.73	$116.75	$116.70
Purchase #4	$91.78	3.206%	$94.7225	$94.72	$94.70	$94.70
Purchase #5	$43.62	4.518%	$45.5908	$45.59	$45.60	$45.60
Purchase #6	$134.82	3.150%	$139.0668	$139.07	$139.05	$139.10
Purchase #7	$53.56	5.767%	$56.6488	$56.65	$56.65	$56.60
7 purchase totals =	$839.48		$900.2753	$900.28	$900.30	$900.20