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	$153.47	8.821%	$167.0076	$167.01	$167.00	$167.00
Purchase #2	$12.78	4.700%	$13.3807	$13.38	$13.40	$13.40
Purchase #3	$62.71	3.334%	$64.8008	$64.80	$64.80	$64.80
Purchase #4	$136.80	6.631%	$145.8712	$145.87	$145.85	$145.90
Purchase #5	$35.57	4.732%	$37.2532	$37.25	$37.25	$37.30
Purchase #6	$105.87	9.633%	$116.0685	$116.07	$116.05	$116.10
Purchase #7	$28.55	13.189%	$32.3155	$32.32	$32.30	$32.30
7 purchase totals =	$535.75		$576.6975	$576.70	$576.65	$576.80