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	$142.57	7.473%	$153.2243	$153.22	$153.20	$153.20
Purchase #2	$62.56	6.114%	$66.3849	$66.38	$66.40	$66.40
Purchase #3	$86.91	6.676%	$92.7121	$92.71	$92.70	$92.70
Purchase #4	$242.59	9.178%	$264.8549	$264.85	$264.85	$264.90
Purchase #5	$220.49	5.109%	$231.7548	$231.75	$231.75	$231.80
Purchase #6	$237.92	3.111%	$245.3217	$245.32	$245.30	$245.30
Purchase #7	$195.62	13.622%	$222.2674	$222.27	$222.25	$222.30
7 purchase totals =	$1,188.66		$1,276.5201	$1,276.50	$1,276.45	$1,276.60