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	$187.44	11.689%	$209.3499	$209.35	$209.35	$209.30
Purchase #2	$143.98	6.210%	$152.9212	$152.92	$152.90	$152.90
Purchase #3	$169.36	5.107%	$178.0092	$178.01	$178.00	$178.00
Purchase #4	$193.51	3.139%	$199.5843	$199.58	$199.60	$199.60
Purchase #5	$95.76	5.254%	$100.7912	$100.79	$100.80	$100.80
Purchase #6	$10.34	4.508%	$10.8061	$10.81	$10.80	$10.80
Purchase #7	$72.28	7.177%	$77.4675	$77.47	$77.45	$77.50
7 purchase totals =	$872.67		$928.9294	$928.93	$928.90	$928.90