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	$158.81	8.465%	$172.2533	$172.25	$172.25	$172.30
Purchase #2	$103.97	11.484%	$115.9099	$115.91	$115.90	$115.90
Purchase #3	$106.90	12.248%	$119.9931	$119.99	$120.00	$120.00
Purchase #4	$244.63	3.641%	$253.537	$253.54	$253.55	$253.50
Purchase #5	$96.67	3.563%	$100.1144	$100.11	$100.10	$100.10
Purchase #6	$152.57	3.455%	$157.8413	$157.84	$157.85	$157.80
Purchase #7	$87.93	13.477%	$99.7803	$99.78	$99.80	$99.80
7 purchase totals =	$951.48		$1,019.4293	$1,019.42	$1,019.45	$1,019.40