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	$174.79	11.148%	$194.2756	$194.28	$194.30	$194.30
Purchase #2	$249.63	10.178%	$275.0373	$275.04	$275.05	$275.00
Purchase #3	$42.80	3.739%	$44.4003	$44.40	$44.40	$44.40
Purchase #4	$198.61	5.134%	$208.8066	$208.81	$208.80	$208.80
Purchase #5	$37.50	13.658%	$42.6218	$42.62	$42.60	$42.60
Purchase #6	$54.82	10.380%	$60.5103	$60.51	$60.50	$60.50
Purchase #7	$115.56	10.525%	$127.7227	$127.72	$127.70	$127.70
7 purchase totals =	$873.71		$953.3746	$953.38	$953.35	$953.30