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	$213.62	9.620%	$234.1702	$234.17	$234.15	$234.20
Purchase #2	$133.62	9.338%	$146.0974	$146.10	$146.10	$146.10
Purchase #3	$79.62	12.235%	$89.3615	$89.36	$89.35	$89.40
Purchase #4	$174.31	6.206%	$185.1277	$185.13	$185.15	$185.10
Purchase #5	$109.67	6.518%	$116.8183	$116.82	$116.80	$116.80
Purchase #6	$37.35	10.687%	$41.3416	$41.34	$41.35	$41.30
Purchase #7	$47.96	3.433%	$49.6065	$49.61	$49.60	$49.60
7 purchase totals =	$796.15		$862.5232	$862.53	$862.50	$862.50