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	$51.29	7.763%	$55.2716	$55.27	$55.25	$55.30
Purchase #2	$192.98	13.566%	$219.1597	$219.16	$219.15	$219.20
Purchase #3	$118.61	13.150%	$134.2072	$134.21	$134.20	$134.20
Purchase #4	$77.75	6.243%	$82.6039	$82.60	$82.60	$82.60
Purchase #5	$58.54	6.545%	$62.3714	$62.37	$62.35	$62.40
Purchase #6	$109.39	4.835%	$114.679	$114.68	$114.70	$114.70
Purchase #7	$118.93	4.229%	$123.9595	$123.96	$123.95	$124.00
7 purchase totals =	$727.49		$792.2523	$792.25	$792.20	$792.40