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	$134.77	7.775%	$145.2484	$145.25	$145.25	$145.20
Purchase #2	$27.69	12.608%	$31.1812	$31.18	$31.20	$31.20
Purchase #3	$24.61	5.209%	$25.8919	$25.89	$25.90	$25.90
Purchase #4	$59.32	13.338%	$67.2321	$67.23	$67.25	$67.20
Purchase #5	$123.53	8.361%	$133.8583	$133.86	$133.85	$133.90
Purchase #6	$164.36	4.667%	$172.0307	$172.03	$172.05	$172.00
Purchase #7	$119.32	6.708%	$127.324	$127.32	$127.30	$127.30
7 purchase totals =	$653.60		$702.7666	$702.76	$702.80	$702.70