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	$101.62	11.542%	$113.349	$113.35	$113.35	$113.30
Purchase #2	$243.89	4.522%	$254.9187	$254.92	$254.90	$254.90
Purchase #3	$121.41	10.384%	$134.0172	$134.02	$134.00	$134.00
Purchase #4	$156.98	12.854%	$177.1582	$177.16	$177.15	$177.20
Purchase #5	$79.50	5.164%	$83.6054	$83.61	$83.60	$83.60
Purchase #6	$132.80	6.791%	$141.8184	$141.82	$141.80	$141.80
Purchase #7	$144.59	8.377%	$156.7023	$156.70	$156.70	$156.70
7 purchase totals =	$980.79		$1,061.5692	$1,061.58	$1,061.50	$1,061.50