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	$121.81	4.548%	$127.3499	$127.35	$127.35	$127.30
Purchase #2	$181.38	5.675%	$191.6733	$191.67	$191.65	$191.70
Purchase #3	$249.27	9.217%	$272.2452	$272.25	$272.25	$272.20
Purchase #4	$170.33	10.586%	$188.3611	$188.36	$188.35	$188.40
Purchase #5	$78.66	3.285%	$81.244	$81.24	$81.25	$81.20
Purchase #6	$29.34	11.171%	$32.6176	$32.62	$32.60	$32.60
Purchase #7	$53.94	11.471%	$60.1275	$60.13	$60.15	$60.10
7 purchase totals =	$884.73		$953.6186	$953.62	$953.60	$953.50