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	$162.74	10.264%	$179.4436	$179.44	$179.45	$179.40
Purchase #2	$144.27	12.193%	$161.8608	$161.86	$161.85	$161.90
Purchase #3	$148.34	10.730%	$164.2569	$164.26	$164.25	$164.30
Purchase #4	$92.55	10.139%	$101.9336	$101.93	$101.95	$101.90
Purchase #5	$38.38	13.371%	$43.5118	$43.51	$43.50	$43.50
Purchase #6	$114.25	6.153%	$121.2798	$121.28	$121.30	$121.30
Purchase #7	$39.93	7.390%	$42.8808	$42.88	$42.90	$42.90
7 purchase totals =	$740.46		$815.1673	$815.16	$815.20	$815.20