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	$167.33	6.408%	$178.0525	$178.05	$178.05	$178.10
Purchase #2	$120.85	11.522%	$134.7743	$134.77	$134.75	$134.80
Purchase #3	$21.55	3.588%	$22.3232	$22.32	$22.30	$22.30
Purchase #4	$179.62	9.590%	$196.8456	$196.85	$196.85	$196.80
Purchase #5	$247.86	4.252%	$258.399	$258.40	$258.40	$258.40
Purchase #6	$173.53	13.481%	$196.9236	$196.92	$196.90	$196.90
Purchase #7	$33.39	4.241%	$34.8061	$34.81	$34.80	$34.80
7 purchase totals =	$944.13		$1,022.1243	$1,022.12	$1,022.05	$1,022.10