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	$47.77	8.861%	$52.0029	$52.00	$52.00	$52.00
Purchase #2	$164.27	3.338%	$169.7533	$169.75	$169.75	$169.80
Purchase #3	$185.98	5.660%	$196.5065	$196.51	$196.50	$196.50
Purchase #4	$123.56	3.530%	$127.9217	$127.92	$127.90	$127.90
Purchase #5	$217.62	5.845%	$230.3399	$230.34	$230.35	$230.30
Purchase #6	$245.52	7.433%	$263.7695	$263.77	$263.75	$263.80
Purchase #7	$126.37	11.758%	$141.2286	$141.23	$141.25	$141.20
7 purchase totals =	$1,111.09		$1,181.5224	$1,181.52	$1,181.50	$1,181.50