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	$146.74	6.362%	$156.0756	$156.08	$156.10	$156.10
Purchase #2	$191.48	3.682%	$198.5303	$198.53	$198.55	$198.50
Purchase #3	$33.84	10.113%	$37.2622	$37.26	$37.25	$37.30
Purchase #4	$132.85	10.222%	$146.4299	$146.43	$146.45	$146.40
Purchase #5	$31.73	4.127%	$33.0395	$33.04	$33.05	$33.00
Purchase #6	$74.66	6.224%	$79.3068	$79.31	$79.30	$79.30
Purchase #7	$134.30	8.645%	$145.9102	$145.91	$145.90	$145.90
7 purchase totals =	$745.60		$796.5545	$796.56	$796.60	$796.50