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	$200.72	10.422%	$221.639	$221.64	$221.65	$221.60
Purchase #2	$158.67	9.582%	$173.8738	$173.87	$173.85	$173.90
Purchase #3	$144.58	12.230%	$162.2621	$162.26	$162.25	$162.30
Purchase #4	$144.38	11.400%	$160.8393	$160.84	$160.85	$160.80
Purchase #5	$90.62	4.845%	$95.0105	$95.01	$95.00	$95.00
Purchase #6	$36.90	9.769%	$40.5048	$40.50	$40.50	$40.50
Purchase #7	$187.77	11.123%	$208.6557	$208.66	$208.65	$208.70
7 purchase totals =	$963.64		$1,062.7852	$1,062.78	$1,062.75	$1,062.80