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	$58.96	11.126%	$65.5199	$65.52	$65.50	$65.50
Purchase #2	$96.59	12.370%	$108.5382	$108.54	$108.55	$108.50
Purchase #3	$143.96	12.246%	$161.5893	$161.59	$161.60	$161.60
Purchase #4	$165.68	4.184%	$172.6121	$172.61	$172.60	$172.60
Purchase #5	$237.98	12.663%	$268.1154	$268.12	$268.10	$268.10
Purchase #6	$122.71	7.342%	$131.7194	$131.72	$131.70	$131.70
Purchase #7	$233.67	3.468%	$241.7737	$241.77	$241.75	$241.80
7 purchase totals =	$1,059.55		$1,149.8680	$1,149.87	$1,149.80	$1,149.80