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	$56.89	4.807%	$59.6247	$59.62	$59.60	$59.60
Purchase #2	$83.86	3.545%	$86.8328	$86.83	$86.85	$86.80
Purchase #3	$224.79	13.246%	$254.5657	$254.57	$254.55	$254.60
Purchase #4	$246.65	13.339%	$279.5506	$279.55	$279.55	$279.60
Purchase #5	$169.69	8.842%	$184.694	$184.69	$184.70	$184.70
Purchase #6	$99.84	4.574%	$104.4067	$104.41	$104.40	$104.40
Purchase #7	$60.30	6.246%	$64.0663	$64.07	$64.05	$64.10
7 purchase totals =	$942.02		$1,033.7408	$1,033.74	$1,033.70	$1,033.80