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	$213.45	4.751%	$223.591	$223.59	$223.60	$223.60
Purchase #2	$131.98	7.137%	$141.3994	$141.40	$141.40	$141.40
Purchase #3	$17.67	4.626%	$18.4874	$18.49	$18.50	$18.50
Purchase #4	$7.44	6.377%	$7.9144	$7.91	$7.90	$7.90
Purchase #5	$133.63	10.189%	$147.2456	$147.25	$147.25	$147.20
Purchase #6	$200.40	4.324%	$209.0653	$209.07	$209.05	$209.10
Purchase #7	$9.89	10.475%	$10.926	$10.93	$10.95	$10.90
7 purchase totals =	$714.46		$758.6291	$758.64	$758.65	$758.60