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	$103.83	7.152%	$111.2559	$111.26	$111.25	$111.30
Purchase #2	$86.70	12.305%	$97.3684	$97.37	$97.35	$97.40
Purchase #3	$99.82	6.741%	$106.5489	$106.55	$106.55	$106.50
Purchase #4	$173.59	8.802%	$188.8694	$188.87	$188.85	$188.90
Purchase #5	$189.67	10.415%	$209.4241	$209.42	$209.40	$209.40
Purchase #6	$153.83	7.792%	$165.8164	$165.82	$165.80	$165.80
Purchase #7	$223.62	6.870%	$238.9827	$238.98	$239.00	$239.00
7 purchase totals =	$1,031.06		$1,118.2658	$1,118.27	$1,118.20	$1,118.30