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	$32.38	10.694%	$35.8427	$35.84	$35.85	$35.80
Purchase #2	$242.60	13.591%	$275.5718	$275.57	$275.55	$275.60
Purchase #3	$166.37	3.432%	$172.0798	$172.08	$172.10	$172.10
Purchase #4	$244.94	6.585%	$261.0693	$261.07	$261.05	$261.10
Purchase #5	$214.76	4.228%	$223.8401	$223.84	$223.85	$223.80
Purchase #6	$12.81	8.303%	$13.8736	$13.87	$13.85	$13.90
Purchase #7	$35.37	11.233%	$39.3431	$39.34	$39.35	$39.30
7 purchase totals =	$949.23		$1,021.6204	$1,021.61	$1,021.60	$1,021.60