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	$78.39	12.647%	$88.304	$88.30	$88.30	$88.30
Purchase #2	$240.47	9.116%	$262.3912	$262.39	$262.40	$262.40
Purchase #3	$201.29	6.435%	$214.243	$214.24	$214.25	$214.20
Purchase #4	$152.86	12.642%	$172.1846	$172.18	$172.20	$172.20
Purchase #5	$68.85	13.307%	$78.0119	$78.01	$78.00	$78.00
Purchase #6	$179.63	7.483%	$193.0717	$193.07	$193.05	$193.10
Purchase #7	$172.42	9.150%	$188.1964	$188.20	$188.20	$188.20
7 purchase totals =	$1,093.91		$1,196.4028	$1,196.39	$1,196.40	$1,196.40