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	$10.45	12.709%	$11.7781	$11.78	$11.80	$11.80
Purchase #2	$26.28	3.321%	$27.1528	$27.15	$27.15	$27.20
Purchase #3	$53.33	3.332%	$55.107	$55.11	$55.10	$55.10
Purchase #4	$250.59	6.230%	$266.2018	$266.20	$266.20	$266.20
Purchase #5	$238.77	12.492%	$268.5971	$268.60	$268.60	$268.60
Purchase #6	$248.42	9.461%	$271.923	$271.92	$271.90	$271.90
Purchase #7	$170.52	8.213%	$184.5248	$184.52	$184.50	$184.50
7 purchase totals =	$998.36		$1,085.2846	$1,085.28	$1,085.25	$1,085.30