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	$112.32	13.852%	$127.8786	$127.88	$127.90	$127.90
Purchase #2	$64.42	9.541%	$70.5663	$70.57	$70.55	$70.60
Purchase #3	$168.76	3.375%	$174.4557	$174.46	$174.45	$174.50
Purchase #4	$154.55	3.273%	$159.6084	$159.61	$159.60	$159.60
Purchase #5	$111.49	9.665%	$122.2655	$122.27	$122.25	$122.30
Purchase #6	$43.56	12.764%	$49.12	$49.12	$49.10	$49.10
Purchase #7	$28.69	12.460%	$32.2648	$32.26	$32.25	$32.30
7 purchase totals =	$683.79		$736.1593	$736.17	$736.10	$736.30