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	$101.41	8.408%	$109.9366	$109.94	$109.95	$109.90
Purchase #2	$134.43	12.753%	$151.5739	$151.57	$151.55	$151.60
Purchase #3	$149.80	7.588%	$161.1668	$161.17	$161.15	$161.20
Purchase #4	$130.90	10.862%	$145.1184	$145.12	$145.10	$145.10
Purchase #5	$18.51	13.479%	$21.005	$21.01	$21.00	$21.00
Purchase #6	$91.70	3.170%	$94.6069	$94.61	$94.60	$94.60
Purchase #7	$37.95	3.361%	$39.2255	$39.23	$39.25	$39.20
7 purchase totals =	$664.70		$722.6331	$722.65	$722.60	$722.60