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	$41.59	9.467%	$45.5273	$45.53	$45.55	$45.50
Purchase #2	$112.41	13.290%	$127.3493	$127.35	$127.35	$127.30
Purchase #3	$96.45	11.447%	$107.4906	$107.49	$107.50	$107.50
Purchase #4	$16.77	13.413%	$19.0194	$19.02	$19.00	$19.00
Purchase #5	$197.91	4.224%	$206.2697	$206.27	$206.25	$206.30
Purchase #6	$38.59	4.409%	$40.2914	$40.29	$40.30	$40.30
Purchase #7	$157.73	5.653%	$166.6465	$166.65	$166.65	$166.60
7 purchase totals =	$661.45		$712.5942	$712.60	$712.60	$712.50