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	$244.39	5.650%	$258.198	$258.20	$258.20	$258.20
Purchase #2	$39.70	3.698%	$41.1681	$41.17	$41.15	$41.20
Purchase #3	$86.79	4.760%	$90.9212	$90.92	$90.90	$90.90
Purchase #4	$240.44	4.231%	$250.613	$250.61	$250.60	$250.60
Purchase #5	$151.37	10.854%	$167.7997	$167.80	$167.80	$167.80
Purchase #6	$93.45	10.465%	$103.2295	$103.23	$103.25	$103.20
Purchase #7	$194.58	12.181%	$218.2818	$218.28	$218.30	$218.30
7 purchase totals =	$1,050.72		$1,130.2113	$1,130.21	$1,130.20	$1,130.20