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	$162.38	6.530%	$172.9834	$172.98	$173.00	$173.00
Purchase #2	$229.79	11.270%	$255.6873	$255.69	$255.70	$255.70
Purchase #3	$154.96	9.861%	$170.2406	$170.24	$170.25	$170.20
Purchase #4	$162.96	13.777%	$185.411	$185.41	$185.40	$185.40
Purchase #5	$106.95	3.406%	$110.5927	$110.59	$110.60	$110.60
Purchase #6	$38.77	6.867%	$41.4323	$41.43	$41.45	$41.40
Purchase #7	$138.57	5.273%	$145.8768	$145.88	$145.90	$145.90
7 purchase totals =	$994.38		$1,082.2241	$1,082.22	$1,082.30	$1,082.20