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	$34.59	8.662%	$37.5862	$37.59	$37.60	$37.60
Purchase #2	$76.71	12.300%	$86.1453	$86.15	$86.15	$86.10
Purchase #3	$54.31	8.651%	$59.0084	$59.01	$59.00	$59.00
Purchase #4	$201.27	9.409%	$220.2075	$220.21	$220.20	$220.20
Purchase #5	$240.74	6.484%	$256.3496	$256.35	$256.35	$256.30
Purchase #6	$216.38	3.699%	$224.3839	$224.38	$224.40	$224.40
Purchase #7	$149.46	6.777%	$159.5889	$159.59	$159.60	$159.60
7 purchase totals =	$973.46		$1,043.2698	$1,043.28	$1,043.30	$1,043.20