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	$67.90	13.168%	$76.8411	$76.84	$76.85	$76.80
Purchase #2	$96.75	4.834%	$101.4269	$101.43	$101.45	$101.40
Purchase #3	$20.43	8.235%	$22.1124	$22.11	$22.10	$22.10
Purchase #4	$236.91	7.767%	$255.3108	$255.31	$255.30	$255.30
Purchase #5	$101.82	10.553%	$112.5651	$112.57	$112.55	$112.60
Purchase #6	$133.90	5.518%	$141.2886	$141.29	$141.30	$141.30
Purchase #7	$164.64	4.841%	$172.6102	$172.61	$172.60	$172.60
7 purchase totals =	$822.35		$882.1551	$882.16	$882.15	$882.10