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	$194.65	10.587%	$215.2576	$215.26	$215.25	$215.30
Purchase #2	$81.54	8.514%	$88.4823	$88.48	$88.50	$88.50
Purchase #3	$87.72	5.182%	$92.2657	$92.27	$92.25	$92.30
Purchase #4	$173.99	6.470%	$185.2472	$185.25	$185.25	$185.20
Purchase #5	$140.48	8.726%	$152.7383	$152.74	$152.75	$152.70
Purchase #6	$54.47	11.108%	$60.5205	$60.52	$60.50	$60.50
Purchase #7	$100.52	12.202%	$112.7855	$112.79	$112.80	$112.80
7 purchase totals =	$833.37		$907.2971	$907.31	$907.30	$907.30