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	$159.60	4.322%	$166.4979	$166.50	$166.50	$166.50
Purchase #2	$113.32	4.428%	$118.3378	$118.34	$118.35	$118.30
Purchase #3	$83.33	13.107%	$94.2521	$94.25	$94.25	$94.30
Purchase #4	$34.27	7.477%	$36.8324	$36.83	$36.85	$36.80
Purchase #5	$224.69	7.429%	$241.3822	$241.38	$241.40	$241.40
Purchase #6	$185.62	10.709%	$205.498	$205.50	$205.50	$205.50
Purchase #7	$225.30	11.799%	$251.8831	$251.88	$251.90	$251.90
7 purchase totals =	$1,026.13		$1,114.6835	$1,114.68	$1,114.75	$1,114.70