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	$147.52	5.598%	$155.7782	$155.78	$155.80	$155.80
Purchase #2	$210.39	5.707%	$222.397	$222.40	$222.40	$222.40
Purchase #3	$140.93	4.207%	$146.8589	$146.86	$146.85	$146.90
Purchase #4	$123.63	3.476%	$127.9274	$127.93	$127.95	$127.90
Purchase #5	$185.86	3.453%	$192.2777	$192.28	$192.30	$192.30
Purchase #6	$87.83	12.200%	$98.5453	$98.55	$98.55	$98.50
Purchase #7	$92.94	6.816%	$99.2748	$99.27	$99.25	$99.30
7 purchase totals =	$989.10		$1,043.0593	$1,043.07	$1,043.10	$1,043.10