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	$61.66	8.743%	$67.0509	$67.05	$67.05	$67.10
Purchase #2	$208.69	11.762%	$233.2361	$233.24	$233.25	$233.20
Purchase #3	$70.55	12.194%	$79.1529	$79.15	$79.15	$79.20
Purchase #4	$243.60	11.503%	$271.6213	$271.62	$271.60	$271.60
Purchase #5	$173.42	12.399%	$194.9223	$194.92	$194.90	$194.90
Purchase #6	$179.64	10.559%	$198.6082	$198.61	$198.60	$198.60
Purchase #7	$35.90	13.628%	$40.7925	$40.79	$40.80	$40.80
7 purchase totals =	$973.46		$1,085.3842	$1,085.38	$1,085.35	$1,085.40