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	$143.72	12.377%	$161.5082	$161.51	$161.50	$161.50
Purchase #2	$174.87	4.237%	$182.2792	$182.28	$182.30	$182.30
Purchase #3	$39.38	9.401%	$43.0821	$43.08	$43.10	$43.10
Purchase #4	$101.75	11.263%	$113.2101	$113.21	$113.20	$113.20
Purchase #5	$141.51	7.834%	$152.5959	$152.60	$152.60	$152.60
Purchase #6	$206.58	7.336%	$221.7347	$221.73	$221.75	$221.70
Purchase #7	$152.74	13.184%	$172.8772	$172.88	$172.90	$172.90
7 purchase totals =	$960.55		$1,047.2874	$1,047.29	$1,047.35	$1,047.30