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	$133.47	8.713%	$145.0992	$145.10	$145.10	$145.10
Purchase #2	$233.84	9.189%	$255.3276	$255.33	$255.35	$255.30
Purchase #3	$203.42	13.325%	$230.5257	$230.53	$230.55	$230.50
Purchase #4	$159.76	4.122%	$166.3453	$166.35	$166.35	$166.30
Purchase #5	$53.50	7.574%	$57.5521	$57.55	$57.55	$57.60
Purchase #6	$233.78	10.712%	$258.8225	$258.82	$258.80	$258.80
Purchase #7	$174.58	6.479%	$185.891	$185.89	$185.90	$185.90
7 purchase totals =	$1,192.35		$1,299.5634	$1,299.57	$1,299.60	$1,299.50