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	$146.71	5.495%	$154.7717	$154.77	$154.75	$154.80
Purchase #2	$116.63	12.707%	$131.4502	$131.45	$131.45	$131.50
Purchase #3	$93.73	5.242%	$98.6433	$98.64	$98.65	$98.60
Purchase #4	$32.96	13.415%	$37.3816	$37.38	$37.40	$37.40
Purchase #5	$5.29	5.163%	$5.5631	$5.56	$5.55	$5.60
Purchase #6	$139.95	8.287%	$151.5477	$151.55	$151.55	$151.50
Purchase #7	$101.80	11.361%	$113.3655	$113.37	$113.35	$113.40
7 purchase totals =	$637.07		$692.7231	$692.72	$692.70	$692.80