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	$229.52	3.431%	$237.3948	$237.39	$237.40	$237.40
Purchase #2	$143.88	6.742%	$153.5804	$153.58	$153.60	$153.60
Purchase #3	$177.41	10.810%	$196.588	$196.59	$196.60	$196.60
Purchase #4	$138.70	6.715%	$148.0137	$148.01	$148.00	$148.00
Purchase #5	$191.83	3.868%	$199.25	$199.25	$199.25	$199.30
Purchase #6	$64.98	7.328%	$69.7417	$69.74	$69.75	$69.70
Purchase #7	$127.38	12.124%	$142.8236	$142.82	$142.80	$142.80
7 purchase totals =	$1,073.70		$1,147.3922	$1,147.38	$1,147.40	$1,147.40