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	$225.54	4.556%	$235.8156	$235.82	$235.80	$235.80
Purchase #2	$25.35	11.328%	$28.2216	$28.22	$28.20	$28.20
Purchase #3	$9.30	12.351%	$10.4486	$10.45	$10.45	$10.40
Purchase #4	$152.26	8.484%	$165.1777	$165.18	$165.20	$165.20
Purchase #5	$140.89	8.211%	$152.4585	$152.46	$152.45	$152.50
Purchase #6	$121.72	9.135%	$132.8391	$132.84	$132.85	$132.80
Purchase #7	$185.52	3.224%	$191.5012	$191.50	$191.50	$191.50
7 purchase totals =	$860.58		$916.4623	$916.47	$916.45	$916.40