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	$127.50	13.830%	$145.1333	$145.13	$145.15	$145.10
Purchase #2	$127.77	12.346%	$143.5445	$143.54	$143.55	$143.50
Purchase #3	$36.36	7.160%	$38.9634	$38.96	$38.95	$39.00
Purchase #4	$57.86	9.244%	$63.2086	$63.21	$63.20	$63.20
Purchase #5	$34.88	13.865%	$39.7161	$39.72	$39.70	$39.70
Purchase #6	$103.37	11.142%	$114.8875	$114.89	$114.90	$114.90
Purchase #7	$124.96	9.751%	$137.1448	$137.14	$137.15	$137.10
7 purchase totals =	$612.70		$682.5982	$682.59	$682.60	$682.50