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	$154.86	11.109%	$172.0634	$172.06	$172.05	$172.10
Purchase #2	$197.74	4.526%	$206.6897	$206.69	$206.70	$206.70
Purchase #3	$167.62	6.465%	$178.4566	$178.46	$178.45	$178.50
Purchase #4	$77.55	7.577%	$83.426	$83.43	$83.45	$83.40
Purchase #5	$232.69	6.577%	$247.994	$247.99	$248.00	$248.00
Purchase #6	$136.32	3.480%	$141.0639	$141.06	$141.05	$141.10
Purchase #7	$61.90	8.523%	$67.1757	$67.18	$67.20	$67.20
7 purchase totals =	$1,028.68		$1,096.8693	$1,096.87	$1,096.90	$1,097.00