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	$76.69	13.205%	$86.8169	$86.82	$86.80	$86.80
Purchase #2	$209.42	6.184%	$222.3705	$222.37	$222.35	$222.40
Purchase #3	$250.45	9.748%	$274.8639	$274.86	$274.85	$274.90
Purchase #4	$65.58	8.814%	$71.3602	$71.36	$71.35	$71.40
Purchase #5	$106.97	3.785%	$111.0188	$111.02	$111.00	$111.00
Purchase #6	$58.77	3.660%	$60.921	$60.92	$60.90	$60.90
Purchase #7	$57.97	13.125%	$65.5786	$65.58	$65.60	$65.60
7 purchase totals =	$825.85		$892.9299	$892.93	$892.85	$893.00