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	$196.26	5.586%	$207.2231	$207.22	$207.20	$207.20
Purchase #2	$71.80	13.561%	$81.5368	$81.54	$81.55	$81.50
Purchase #3	$37.77	6.504%	$40.2266	$40.23	$40.25	$40.20
Purchase #4	$70.49	10.813%	$78.1121	$78.11	$78.10	$78.10
Purchase #5	$108.91	4.456%	$113.763	$113.76	$113.75	$113.80
Purchase #6	$69.32	13.206%	$78.4744	$78.47	$78.45	$78.50
Purchase #7	$148.43	3.470%	$153.5805	$153.58	$153.60	$153.60
7 purchase totals =	$702.98		$752.9165	$752.91	$752.90	$752.90