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	$119.28	4.272%	$124.3756	$124.38	$124.40	$124.40
Purchase #2	$167.37	13.492%	$189.9516	$189.95	$189.95	$190.00
Purchase #3	$236.82	10.287%	$261.1817	$261.18	$261.20	$261.20
Purchase #4	$190.70	10.810%	$211.3147	$211.31	$211.30	$211.30
Purchase #5	$184.39	3.536%	$190.91	$190.91	$190.90	$190.90
Purchase #6	$228.82	11.499%	$255.132	$255.13	$255.15	$255.10
Purchase #7	$102.29	7.310%	$109.7674	$109.77	$109.75	$109.80
7 purchase totals =	$1,229.67		$1,342.6330	$1,342.63	$1,342.65	$1,342.70