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	$145.47	4.113%	$151.4532	$151.45	$151.45	$151.50
Purchase #2	$190.39	3.362%	$196.7909	$196.79	$196.80	$196.80
Purchase #3	$138.29	10.221%	$152.4246	$152.42	$152.40	$152.40
Purchase #4	$168.36	8.686%	$182.9837	$182.98	$183.00	$183.00
Purchase #5	$82.41	8.123%	$89.1042	$89.10	$89.10	$89.10
Purchase #6	$132.76	5.201%	$139.6648	$139.66	$139.65	$139.70
Purchase #7	$222.96	10.177%	$245.6506	$245.65	$245.65	$245.70
7 purchase totals =	$1,080.64		$1,158.0720	$1,158.05	$1,158.05	$1,158.20