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	$134.32	13.173%	$152.014	$152.01	$152.00	$152.00
Purchase #2	$32.86	9.863%	$36.101	$36.10	$36.10	$36.10
Purchase #3	$94.47	4.547%	$98.7656	$98.77	$98.75	$98.80
Purchase #4	$236.47	5.698%	$249.9441	$249.94	$249.95	$249.90
Purchase #5	$145.52	3.521%	$150.6438	$150.64	$150.65	$150.60
Purchase #6	$99.43	11.495%	$110.8595	$110.86	$110.85	$110.90
Purchase #7	$103.49	5.861%	$109.5555	$109.56	$109.55	$109.60
7 purchase totals =	$846.56		$907.8835	$907.88	$907.85	$907.90