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	$202.93	3.397%	$209.8235	$209.82	$209.80	$209.80
Purchase #2	$199.28	7.661%	$214.5468	$214.55	$214.55	$214.50
Purchase #3	$143.42	5.454%	$151.2421	$151.24	$151.25	$151.20
Purchase #4	$17.57	4.451%	$18.352	$18.35	$18.35	$18.40
Purchase #5	$64.74	11.624%	$72.2654	$72.27	$72.25	$72.30
Purchase #6	$52.34	13.463%	$59.3865	$59.39	$59.40	$59.40
Purchase #7	$80.87	6.308%	$85.9713	$85.97	$85.95	$86.00
7 purchase totals =	$761.15		$811.5876	$811.59	$811.55	$811.60