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	$153.43	4.710%	$160.6566	$160.66	$160.65	$160.70
Purchase #2	$192.33	12.601%	$216.5655	$216.57	$216.55	$216.60
Purchase #3	$58.80	6.409%	$62.5685	$62.57	$62.55	$62.60
Purchase #4	$88.53	6.672%	$94.4367	$94.44	$94.45	$94.40
Purchase #5	$101.54	9.337%	$111.0208	$111.02	$111.00	$111.00
Purchase #6	$101.68	11.390%	$113.2614	$113.26	$113.25	$113.30
Purchase #7	$87.25	3.584%	$90.377	$90.38	$90.40	$90.40
7 purchase totals =	$783.56		$848.8865	$848.90	$848.85	$849.00