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	$185.62	10.613%	$205.3199	$205.32	$205.30	$205.30
Purchase #2	$18.71	8.626%	$20.3239	$20.32	$20.30	$20.30
Purchase #3	$98.39	11.355%	$109.5622	$109.56	$109.55	$109.60
Purchase #4	$126.98	5.763%	$134.2979	$134.30	$134.30	$134.30
Purchase #5	$178.47	6.640%	$190.3204	$190.32	$190.30	$190.30
Purchase #6	$118.28	8.660%	$128.523	$128.52	$128.50	$128.50
Purchase #7	$163.39	10.194%	$180.046	$180.05	$180.05	$180.00
7 purchase totals =	$889.84		$968.3933	$968.39	$968.30	$968.30