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	$68.61	4.424%	$71.6453	$71.65	$71.65	$71.60
Purchase #2	$102.95	8.465%	$111.6647	$111.66	$111.65	$111.70
Purchase #3	$61.94	5.338%	$65.2464	$65.25	$65.25	$65.20
Purchase #4	$111.68	4.716%	$116.9468	$116.95	$116.95	$116.90
Purchase #5	$160.78	5.612%	$169.803	$169.80	$169.80	$169.80
Purchase #6	$209.65	7.407%	$225.1788	$225.18	$225.20	$225.20
Purchase #7	$10.85	13.745%	$12.3413	$12.34	$12.35	$12.30
7 purchase totals =	$726.46		$772.8263	$772.83	$772.85	$772.70