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	$221.47	5.452%	$233.5445	$233.54	$233.55	$233.50
Purchase #2	$173.76	4.227%	$181.1048	$181.10	$181.10	$181.10
Purchase #3	$117.53	8.381%	$127.3802	$127.38	$127.40	$127.40
Purchase #4	$130.27	12.794%	$146.9367	$146.94	$146.95	$146.90
Purchase #5	$78.94	4.540%	$82.5239	$82.52	$82.50	$82.50
Purchase #6	$242.48	8.792%	$263.7988	$263.80	$263.80	$263.80
Purchase #7	$193.82	9.295%	$211.8356	$211.84	$211.85	$211.80
7 purchase totals =	$1,158.27		$1,247.1245	$1,247.12	$1,247.15	$1,247.00