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	$127.65	7.609%	$137.3629	$137.36	$137.35	$137.40
Purchase #2	$152.37	9.131%	$166.2829	$166.28	$166.30	$166.30
Purchase #3	$221.67	11.491%	$247.1421	$247.14	$247.15	$247.10
Purchase #4	$177.68	10.802%	$196.873	$196.87	$196.85	$196.90
Purchase #5	$91.92	12.544%	$103.4504	$103.45	$103.45	$103.50
Purchase #6	$100.60	3.788%	$104.4107	$104.41	$104.40	$104.40
Purchase #7	$211.28	8.375%	$228.9747	$228.97	$228.95	$229.00
7 purchase totals =	$1,083.17		$1,184.4967	$1,184.48	$1,184.45	$1,184.60