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	$181.54	8.452%	$196.8838	$196.88	$196.90	$196.90
Purchase #2	$40.50	5.166%	$42.5922	$42.59	$42.60	$42.60
Purchase #3	$47.33	3.873%	$49.1631	$49.16	$49.15	$49.20
Purchase #4	$235.52	11.277%	$262.0796	$262.08	$262.10	$262.10
Purchase #5	$151.93	13.565%	$172.5393	$172.54	$172.55	$172.50
Purchase #6	$61.29	7.436%	$65.8475	$65.85	$65.85	$65.80
Purchase #7	$187.73	6.254%	$199.4706	$199.47	$199.45	$199.50
7 purchase totals =	$905.84		$988.5761	$988.57	$988.60	$988.60