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	$41.72	8.608%	$45.3113	$45.31	$45.30	$45.30
Purchase #2	$60.39	13.477%	$68.5288	$68.53	$68.55	$68.50
Purchase #3	$223.97	5.178%	$235.5672	$235.57	$235.55	$235.60
Purchase #4	$199.31	11.691%	$222.6113	$222.61	$222.60	$222.60
Purchase #5	$218.56	5.617%	$230.8365	$230.84	$230.85	$230.80
Purchase #6	$170.61	4.721%	$178.6645	$178.66	$178.65	$178.70
Purchase #7	$54.93	8.861%	$59.7973	$59.80	$59.80	$59.80
7 purchase totals =	$969.49		$1,041.3169	$1,041.32	$1,041.30	$1,041.30