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	$139.98	8.727%	$152.1961	$152.20	$152.20	$152.20
Purchase #2	$211.39	4.778%	$221.4902	$221.49	$221.50	$221.50
Purchase #3	$196.29	11.759%	$219.3717	$219.37	$219.35	$219.40
Purchase #4	$77.65	3.470%	$80.3445	$80.34	$80.35	$80.30
Purchase #5	$240.82	9.376%	$263.3993	$263.40	$263.40	$263.40
Purchase #6	$86.51	9.233%	$94.4975	$94.50	$94.50	$94.50
Purchase #7	$21.65	13.682%	$24.6122	$24.61	$24.60	$24.60
7 purchase totals =	$974.29		$1,055.9115	$1,055.91	$1,055.90	$1,055.90