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	$161.47	8.364%	$174.9754	$174.98	$175.00	$175.00
Purchase #2	$148.79	11.835%	$166.3993	$166.40	$166.40	$166.40
Purchase #3	$150.99	5.255%	$158.9245	$158.92	$158.90	$158.90
Purchase #4	$82.90	9.706%	$90.9463	$90.95	$90.95	$90.90
Purchase #5	$49.33	8.553%	$53.5492	$53.55	$53.55	$53.50
Purchase #6	$137.31	4.287%	$143.1965	$143.20	$143.20	$143.20
Purchase #7	$101.33	6.615%	$108.033	$108.03	$108.05	$108.00
7 purchase totals =	$832.12		$896.0242	$896.03	$896.05	$895.90