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	$69.76	10.810%	$77.3011	$77.30	$77.30	$77.30
Purchase #2	$215.88	9.208%	$235.7582	$235.76	$235.75	$235.80
Purchase #3	$223.61	7.830%	$241.1187	$241.12	$241.10	$241.10
Purchase #4	$50.43	9.282%	$55.1109	$55.11	$55.10	$55.10
Purchase #5	$103.52	10.579%	$114.4714	$114.47	$114.45	$114.50
Purchase #6	$203.45	5.327%	$214.2878	$214.29	$214.30	$214.30
Purchase #7	$57.81	12.864%	$65.2467	$65.25	$65.25	$65.20
7 purchase totals =	$924.46		$1,003.2948	$1,003.30	$1,003.25	$1,003.30