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	$188.70	8.124%	$204.03	$204.03	$204.05	$204.00
Purchase #2	$241.51	5.773%	$255.4524	$255.45	$255.45	$255.50
Purchase #3	$237.69	13.286%	$269.2695	$269.27	$269.25	$269.30
Purchase #4	$65.55	10.860%	$72.6687	$72.67	$72.65	$72.70
Purchase #5	$216.89	7.782%	$233.7684	$233.77	$233.75	$233.80
Purchase #6	$29.27	9.821%	$32.1446	$32.14	$32.15	$32.10
Purchase #7	$135.66	12.725%	$152.9227	$152.92	$152.90	$152.90
7 purchase totals =	$1,115.27		$1,220.2563	$1,220.25	$1,220.20	$1,220.30