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	$224.73	4.485%	$234.8091	$234.81	$234.80	$234.80
Purchase #2	$134.66	8.771%	$146.471	$146.47	$146.45	$146.50
Purchase #3	$123.66	13.466%	$140.3121	$140.31	$140.30	$140.30
Purchase #4	$115.49	7.312%	$123.9346	$123.93	$123.95	$123.90
Purchase #5	$100.65	3.759%	$104.4334	$104.43	$104.45	$104.40
Purchase #6	$143.35	7.207%	$153.6812	$153.68	$153.70	$153.70
Purchase #7	$114.29	7.629%	$123.0092	$123.01	$123.00	$123.00
7 purchase totals =	$956.83		$1,026.6506	$1,026.64	$1,026.65	$1,026.60