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	$71.71	4.801%	$75.1528	$75.15	$75.15	$75.20
Purchase #2	$149.95	10.342%	$165.4578	$165.46	$165.45	$165.50
Purchase #3	$32.88	13.677%	$37.377	$37.38	$37.40	$37.40
Purchase #4	$159.81	4.680%	$167.2891	$167.29	$167.30	$167.30
Purchase #5	$175.52	13.828%	$199.7909	$199.79	$199.80	$199.80
Purchase #6	$59.82	12.589%	$67.3507	$67.35	$67.35	$67.40
Purchase #7	$196.46	4.245%	$204.7997	$204.80	$204.80	$204.80
7 purchase totals =	$846.15		$917.2180	$917.22	$917.25	$917.40