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	$97.35	8.242%	$105.3736	$105.37	$105.35	$105.40
Purchase #2	$15.78	8.637%	$17.1429	$17.14	$17.15	$17.10
Purchase #3	$37.47	8.259%	$40.5646	$40.56	$40.55	$40.60
Purchase #4	$185.84	13.585%	$211.0864	$211.09	$211.10	$211.10
Purchase #5	$172.73	13.679%	$196.3577	$196.36	$196.35	$196.40
Purchase #6	$37.38	10.221%	$41.2006	$41.20	$41.20	$41.20
Purchase #7	$146.92	12.362%	$165.0823	$165.08	$165.10	$165.10
7 purchase totals =	$693.47		$776.8081	$776.80	$776.80	$776.90