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	$59.83	5.408%	$63.0656	$63.07	$63.05	$63.10
Purchase #2	$138.88	7.117%	$148.7641	$148.76	$148.75	$148.80
Purchase #3	$87.82	9.513%	$96.1743	$96.17	$96.15	$96.20
Purchase #4	$94.59	5.393%	$99.6912	$99.69	$99.70	$99.70
Purchase #5	$174.74	6.164%	$185.511	$185.51	$185.50	$185.50
Purchase #6	$64.48	10.337%	$71.1453	$71.15	$71.15	$71.10
Purchase #7	$207.94	9.725%	$228.1622	$228.16	$228.15	$228.20
7 purchase totals =	$828.28		$892.5137	$892.51	$892.45	$892.60