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	$155.58	7.555%	$167.3341	$167.33	$167.35	$167.30
Purchase #2	$162.77	9.595%	$178.3878	$178.39	$178.40	$178.40
Purchase #3	$63.77	4.860%	$66.8692	$66.87	$66.85	$66.90
Purchase #4	$158.91	7.171%	$170.3054	$170.31	$170.30	$170.30
Purchase #5	$101.72	8.172%	$110.0326	$110.03	$110.05	$110.00
Purchase #6	$69.95	12.281%	$78.5406	$78.54	$78.55	$78.50
Purchase #7	$231.29	5.821%	$244.7534	$244.75	$244.75	$244.80
7 purchase totals =	$943.99		$1,016.2231	$1,016.22	$1,016.25	$1,016.20