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	$144.80	11.134%	$160.922	$160.92	$160.90	$160.90
Purchase #2	$195.54	9.626%	$214.3627	$214.36	$214.35	$214.40
Purchase #3	$227.50	6.305%	$241.8439	$241.84	$241.85	$241.80
Purchase #4	$187.91	4.593%	$196.5407	$196.54	$196.55	$196.50
Purchase #5	$155.71	11.862%	$174.1803	$174.18	$174.20	$174.20
Purchase #6	$173.50	3.714%	$179.9438	$179.94	$179.95	$179.90
Purchase #7	$105.63	10.303%	$116.5131	$116.51	$116.50	$116.50
7 purchase totals =	$1,190.59		$1,284.3065	$1,284.29	$1,284.30	$1,284.20