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	$229.33	9.666%	$251.497	$251.50	$251.50	$251.50
Purchase #2	$221.31	9.551%	$242.4473	$242.45	$242.45	$242.40
Purchase #3	$200.35	13.816%	$228.0304	$228.03	$228.05	$228.00
Purchase #4	$224.42	11.627%	$250.5133	$250.51	$250.50	$250.50
Purchase #5	$127.35	12.551%	$143.3337	$143.33	$143.35	$143.30
Purchase #6	$56.88	13.113%	$64.3387	$64.34	$64.35	$64.30
Purchase #7	$156.35	10.534%	$172.8199	$172.82	$172.80	$172.80
7 purchase totals =	$1,215.99		$1,352.9803	$1,352.98	$1,353.00	$1,352.80