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	$32.37	9.857%	$35.5607	$35.56	$35.55	$35.60
Purchase #2	$247.40	9.649%	$271.2716	$271.27	$271.25	$271.30
Purchase #3	$193.58	11.370%	$215.59	$215.59	$215.60	$215.60
Purchase #4	$115.47	10.793%	$127.9327	$127.93	$127.95	$127.90
Purchase #5	$72.54	10.414%	$80.0943	$80.09	$80.10	$80.10
Purchase #6	$71.42	3.800%	$74.134	$74.13	$74.15	$74.10
Purchase #7	$208.95	4.771%	$218.919	$218.92	$218.90	$218.90
7 purchase totals =	$941.73		$1,023.5023	$1,023.49	$1,023.50	$1,023.50