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	$178.64	9.763%	$196.0806	$196.08	$196.10	$196.10
Purchase #2	$213.94	12.241%	$240.1284	$240.13	$240.15	$240.10
Purchase #3	$92.91	6.870%	$99.2929	$99.29	$99.30	$99.30
Purchase #4	$116.82	5.766%	$123.5558	$123.56	$123.55	$123.60
Purchase #5	$222.28	4.648%	$232.6116	$232.61	$232.60	$232.60
Purchase #6	$104.64	12.437%	$117.6541	$117.65	$117.65	$117.70
Purchase #7	$94.43	8.789%	$102.7295	$102.73	$102.75	$102.70
7 purchase totals =	$1,023.66		$1,112.0529	$1,112.05	$1,112.10	$1,112.10