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	$231.56	10.624%	$256.1609	$256.16	$256.15	$256.20
Purchase #2	$186.71	9.237%	$203.9564	$203.96	$203.95	$204.00
Purchase #3	$124.82	7.572%	$134.2714	$134.27	$134.25	$134.30
Purchase #4	$60.69	8.540%	$65.8729	$65.87	$65.85	$65.90
Purchase #5	$124.82	5.653%	$131.8761	$131.88	$131.90	$131.90
Purchase #6	$54.88	8.861%	$59.7429	$59.74	$59.75	$59.70
Purchase #7	$202.91	8.164%	$219.4756	$219.48	$219.50	$219.50
7 purchase totals =	$986.39		$1,071.3562	$1,071.36	$1,071.35	$1,071.50