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	$147.96	7.433%	$158.9579	$158.96	$158.95	$159.00
Purchase #2	$115.58	3.158%	$119.23	$119.23	$119.25	$119.20
Purchase #3	$40.43	6.222%	$42.9456	$42.95	$42.95	$42.90
Purchase #4	$19.57	4.232%	$20.3982	$20.40	$20.40	$20.40
Purchase #5	$86.55	4.747%	$90.6585	$90.66	$90.65	$90.70
Purchase #6	$161.98	3.294%	$167.3156	$167.32	$167.30	$167.30
Purchase #7	$130.30	12.720%	$146.8742	$146.87	$146.85	$146.90
7 purchase totals =	$702.37		$746.3800	$746.39	$746.35	$746.40