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	$87.91	4.613%	$91.9653	$91.97	$91.95	$92.00
Purchase #2	$103.72	12.154%	$116.3261	$116.33	$116.35	$116.30
Purchase #3	$141.26	10.506%	$156.1008	$156.10	$156.10	$156.10
Purchase #4	$46.69	4.277%	$48.6869	$48.69	$48.70	$48.70
Purchase #5	$202.73	10.176%	$223.3598	$223.36	$223.35	$223.40
Purchase #6	$139.70	3.306%	$144.3185	$144.32	$144.30	$144.30
Purchase #7	$234.85	6.726%	$250.646	$250.65	$250.65	$250.60
7 purchase totals =	$956.86		$1,031.4034	$1,031.42	$1,031.40	$1,031.40