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	$197.90	12.379%	$222.398	$222.40	$222.40	$222.40
Purchase #2	$51.85	10.355%	$57.2191	$57.22	$57.20	$57.20
Purchase #3	$130.59	12.363%	$146.7348	$146.73	$146.75	$146.70
Purchase #4	$153.75	4.853%	$161.2115	$161.21	$161.20	$161.20
Purchase #5	$49.34	5.638%	$52.1218	$52.12	$52.10	$52.10
Purchase #6	$150.64	5.109%	$158.3362	$158.34	$158.35	$158.30
Purchase #7	$171.39	4.741%	$179.5156	$179.52	$179.50	$179.50
7 purchase totals =	$905.46		$977.5370	$977.54	$977.50	$977.40