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	$50.71	7.171%	$54.3464	$54.35	$54.35	$54.30
Purchase #2	$38.91	5.867%	$41.1928	$41.19	$41.20	$41.20
Purchase #3	$87.85	4.582%	$91.8753	$91.88	$91.90	$91.90
Purchase #4	$33.83	10.644%	$37.4309	$37.43	$37.45	$37.40
Purchase #5	$161.58	6.729%	$172.4527	$172.45	$172.45	$172.50
Purchase #6	$110.56	12.265%	$124.1202	$124.12	$124.10	$124.10
Purchase #7	$73.28	8.168%	$79.2655	$79.27	$79.25	$79.30
7 purchase totals =	$556.72		$600.6838	$600.69	$600.70	$600.70