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	$118.71	7.276%	$127.3473	$127.35	$127.35	$127.30
Purchase #2	$118.80	3.188%	$122.5873	$122.59	$122.60	$122.60
Purchase #3	$127.92	6.562%	$136.3141	$136.31	$136.30	$136.30
Purchase #4	$67.95	8.797%	$73.9276	$73.93	$73.95	$73.90
Purchase #5	$202.40	4.181%	$210.8623	$210.86	$210.85	$210.90
Purchase #6	$62.37	13.655%	$70.8866	$70.89	$70.90	$70.90
Purchase #7	$96.91	7.828%	$104.4961	$104.50	$104.50	$104.50
7 purchase totals =	$795.06		$846.4213	$846.43	$846.45	$846.40