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	$14.59	5.201%	$15.3488	$15.35	$15.35	$15.30
Purchase #2	$104.53	13.158%	$118.2841	$118.28	$118.30	$118.30
Purchase #3	$74.86	10.526%	$82.7398	$82.74	$82.75	$82.70
Purchase #4	$92.68	11.483%	$103.3224	$103.32	$103.30	$103.30
Purchase #5	$146.48	3.308%	$151.3256	$151.33	$151.35	$151.30
Purchase #6	$60.59	7.823%	$65.33	$65.33	$65.35	$65.30
Purchase #7	$187.82	4.721%	$196.687	$196.69	$196.70	$196.70
7 purchase totals =	$681.55		$733.0377	$733.04	$733.10	$732.90