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	$94.44	5.390%	$99.5303	$99.53	$99.55	$99.50
Purchase #2	$163.46	5.808%	$172.9538	$172.95	$172.95	$173.00
Purchase #3	$73.40	13.532%	$83.3325	$83.33	$83.35	$83.30
Purchase #4	$71.88	6.467%	$76.5285	$76.53	$76.55	$76.50
Purchase #5	$235.83	10.768%	$261.2242	$261.22	$261.20	$261.20
Purchase #6	$90.32	12.426%	$101.5432	$101.54	$101.55	$101.50
Purchase #7	$204.63	12.706%	$230.6303	$230.63	$230.65	$230.60
7 purchase totals =	$933.96		$1,025.7428	$1,025.73	$1,025.80	$1,025.60