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	$83.54	4.821%	$87.5675	$87.57	$87.55	$87.60
Purchase #2	$25.69	9.292%	$28.0771	$28.08	$28.10	$28.10
Purchase #3	$136.38	11.342%	$151.8482	$151.85	$151.85	$151.80
Purchase #4	$127.94	11.600%	$142.781	$142.78	$142.80	$142.80
Purchase #5	$235.64	6.566%	$251.1121	$251.11	$251.10	$251.10
Purchase #6	$148.62	9.604%	$162.8935	$162.89	$162.90	$162.90
Purchase #7	$143.49	10.533%	$158.6038	$158.60	$158.60	$158.60
7 purchase totals =	$901.30		$982.8832	$982.88	$982.90	$982.90