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	$153.98	13.499%	$174.7658	$174.77	$174.75	$174.80
Purchase #2	$150.77	5.753%	$159.4438	$159.44	$159.45	$159.40
Purchase #3	$18.72	11.649%	$20.9007	$20.90	$20.90	$20.90
Purchase #4	$205.38	8.867%	$223.591	$223.59	$223.60	$223.60
Purchase #5	$208.75	9.864%	$229.3411	$229.34	$229.35	$229.30
Purchase #6	$144.58	6.264%	$153.6365	$153.64	$153.65	$153.60
Purchase #7	$12.71	5.594%	$13.421	$13.42	$13.40	$13.40
7 purchase totals =	$894.89		$975.0999	$975.10	$975.10	$975.00