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	$233.39	12.105%	$261.6419	$261.64	$261.65	$261.60
Purchase #2	$64.80	10.257%	$71.4465	$71.45	$71.45	$71.40
Purchase #3	$87.90	4.621%	$91.9619	$91.96	$91.95	$92.00
Purchase #4	$123.88	3.826%	$128.6196	$128.62	$128.60	$128.60
Purchase #5	$52.94	8.404%	$57.3891	$57.39	$57.40	$57.40
Purchase #6	$61.92	6.371%	$65.8649	$65.86	$65.85	$65.90
Purchase #7	$18.90	6.578%	$20.1432	$20.14	$20.15	$20.10
7 purchase totals =	$643.73		$697.0671	$697.06	$697.05	$697.00