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	$30.25	7.455%	$32.5051	$32.51	$32.50	$32.50
Purchase #2	$106.37	7.556%	$114.4073	$114.41	$114.40	$114.40
Purchase #3	$128.27	13.185%	$145.1824	$145.18	$145.20	$145.20
Purchase #4	$203.44	13.378%	$230.6562	$230.66	$230.65	$230.70
Purchase #5	$25.68	7.171%	$27.5215	$27.52	$27.50	$27.50
Purchase #6	$39.90	13.251%	$45.1871	$45.19	$45.20	$45.20
Purchase #7	$179.46	6.173%	$190.5381	$190.54	$190.55	$190.50
7 purchase totals =	$713.37		$785.9977	$786.01	$786.00	$786.00