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	$164.41	5.626%	$173.6597	$173.66	$173.65	$173.70
Purchase #2	$104.32	7.167%	$111.7966	$111.80	$111.80	$111.80
Purchase #3	$67.68	8.144%	$73.1919	$73.19	$73.20	$73.20
Purchase #4	$88.35	12.292%	$99.21	$99.21	$99.20	$99.20
Purchase #5	$57.56	7.525%	$61.8914	$61.89	$61.90	$61.90
Purchase #6	$138.25	3.351%	$142.8828	$142.88	$142.90	$142.90
Purchase #7	$151.57	4.768%	$158.7969	$158.80	$158.80	$158.80
7 purchase totals =	$772.14		$821.4293	$821.43	$821.45	$821.50