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	$140.95	8.601%	$153.0731	$153.07	$153.05	$153.10
Purchase #2	$25.83	12.139%	$28.9655	$28.97	$28.95	$29.00
Purchase #3	$206.87	8.250%	$223.9368	$223.94	$223.95	$223.90
Purchase #4	$96.90	9.221%	$105.8351	$105.84	$105.85	$105.80
Purchase #5	$227.65	4.861%	$238.7161	$238.72	$238.70	$238.70
Purchase #6	$221.79	4.571%	$231.928	$231.93	$231.95	$231.90
Purchase #7	$181.89	4.725%	$190.4843	$190.48	$190.50	$190.50
7 purchase totals =	$1,101.88		$1,172.9389	$1,172.95	$1,172.95	$1,172.90