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	$35.85	3.531%	$37.1159	$37.12	$37.10	$37.10
Purchase #2	$220.44	8.292%	$238.7189	$238.72	$238.70	$238.70
Purchase #3	$154.79	12.169%	$173.6264	$173.63	$173.65	$173.60
Purchase #4	$217.58	10.407%	$240.2236	$240.22	$240.20	$240.20
Purchase #5	$30.44	6.337%	$32.369	$32.37	$32.35	$32.40
Purchase #6	$222.61	6.833%	$237.8209	$237.82	$237.80	$237.80
Purchase #7	$95.38	4.517%	$99.6883	$99.69	$99.70	$99.70
7 purchase totals =	$977.09		$1,059.5630	$1,059.57	$1,059.50	$1,059.50