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	$161.62	7.127%	$173.1387	$173.14	$173.15	$173.10
Purchase #2	$11.43	8.533%	$12.4053	$12.41	$12.40	$12.40
Purchase #3	$29.96	11.852%	$33.5109	$33.51	$33.50	$33.50
Purchase #4	$40.78	10.312%	$44.9852	$44.99	$45.00	$45.00
Purchase #5	$166.69	10.524%	$184.2325	$184.23	$184.25	$184.20
Purchase #6	$245.69	4.129%	$255.8345	$255.83	$255.85	$255.80
Purchase #7	$89.63	11.315%	$99.7716	$99.77	$99.75	$99.80
7 purchase totals =	$745.80		$803.8787	$803.88	$803.90	$803.80