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	$113.83	5.262%	$119.8197	$119.82	$119.80	$119.80
Purchase #2	$156.26	6.811%	$166.9029	$166.90	$166.90	$166.90
Purchase #3	$127.43	13.728%	$144.9236	$144.92	$144.90	$144.90
Purchase #4	$34.44	5.187%	$36.2264	$36.23	$36.25	$36.20
Purchase #5	$79.47	13.601%	$90.2787	$90.28	$90.30	$90.30
Purchase #6	$203.53	5.548%	$214.8218	$214.82	$214.80	$214.80
Purchase #7	$58.86	3.597%	$60.9772	$60.98	$61.00	$61.00
7 purchase totals =	$773.82		$833.9503	$833.95	$833.95	$833.90