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	$206.32	11.691%	$230.4409	$230.44	$230.45	$230.40
Purchase #2	$197.51	8.873%	$215.0351	$215.04	$215.05	$215.00
Purchase #3	$31.39	3.284%	$32.4208	$32.42	$32.40	$32.40
Purchase #4	$247.85	6.734%	$264.5402	$264.54	$264.55	$264.50
Purchase #5	$89.82	13.583%	$102.0203	$102.02	$102.00	$102.00
Purchase #6	$77.51	6.587%	$82.6156	$82.62	$82.60	$82.60
Purchase #7	$40.99	11.532%	$45.717	$45.72	$45.70	$45.70
7 purchase totals =	$891.39		$972.7899	$972.80	$972.75	$972.60