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	$231.98	7.171%	$248.6153	$248.62	$248.60	$248.60
Purchase #2	$79.35	5.738%	$83.9031	$83.90	$83.90	$83.90
Purchase #3	$123.55	13.652%	$140.417	$140.42	$140.40	$140.40
Purchase #4	$94.58	11.559%	$105.5125	$105.51	$105.50	$105.50
Purchase #5	$195.46	11.398%	$217.7385	$217.74	$217.75	$217.70
Purchase #6	$248.65	5.256%	$261.719	$261.72	$261.70	$261.70
Purchase #7	$163.32	5.572%	$172.4202	$172.42	$172.40	$172.40
7 purchase totals =	$1,136.89		$1,230.3256	$1,230.33	$1,230.25	$1,230.20