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	$118.52	8.510%	$128.6061	$128.61	$128.60	$128.60
Purchase #2	$216.38	13.163%	$244.8621	$244.86	$244.85	$244.90
Purchase #3	$17.42	7.278%	$18.6878	$18.69	$18.70	$18.70
Purchase #4	$229.38	9.685%	$251.5955	$251.60	$251.60	$251.60
Purchase #5	$224.38	13.460%	$254.5815	$254.58	$254.60	$254.60
Purchase #6	$127.25	11.269%	$141.5898	$141.59	$141.60	$141.60
Purchase #7	$81.73	4.674%	$85.5501	$85.55	$85.55	$85.60
7 purchase totals =	$1,015.06		$1,125.4729	$1,125.48	$1,125.50	$1,125.60