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	$80.94	13.118%	$91.5577	$91.56	$91.55	$91.60
Purchase #2	$35.55	8.341%	$38.5152	$38.52	$38.50	$38.50
Purchase #3	$109.99	3.776%	$114.1432	$114.14	$114.15	$114.10
Purchase #4	$94.28	11.528%	$105.1486	$105.15	$105.15	$105.10
Purchase #5	$230.98	10.187%	$254.5099	$254.51	$254.50	$254.50
Purchase #6	$25.36	8.265%	$27.456	$27.46	$27.45	$27.50
Purchase #7	$139.72	3.497%	$144.606	$144.61	$144.60	$144.60
7 purchase totals =	$716.82		$775.9366	$775.95	$775.90	$775.90