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	$175.42	12.629%	$197.5738	$197.57	$197.55	$197.60
Purchase #2	$65.62	6.298%	$69.7527	$69.75	$69.75	$69.80
Purchase #3	$214.69	4.302%	$223.926	$223.93	$223.95	$223.90
Purchase #4	$140.59	4.128%	$146.3936	$146.39	$146.40	$146.40
Purchase #5	$88.88	12.366%	$99.8709	$99.87	$99.85	$99.90
Purchase #6	$80.95	11.487%	$90.2487	$90.25	$90.25	$90.20
Purchase #7	$134.55	12.211%	$150.9799	$150.98	$151.00	$151.00
7 purchase totals =	$900.70		$978.7456	$978.74	$978.75	$978.80