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	$74.96	9.865%	$82.3548	$82.35	$82.35	$82.40
Purchase #2	$36.53	4.826%	$38.2929	$38.29	$38.30	$38.30
Purchase #3	$52.77	6.125%	$56.0022	$56.00	$56.00	$56.00
Purchase #4	$28.68	10.779%	$31.7714	$31.77	$31.75	$31.80
Purchase #5	$90.59	12.757%	$102.1466	$102.15	$102.15	$102.10
Purchase #6	$153.77	4.592%	$160.8311	$160.83	$160.85	$160.80
Purchase #7	$37.69	9.375%	$41.2234	$41.22	$41.20	$41.20
7 purchase totals =	$474.99		$512.6224	$512.61	$512.60	$512.60