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	$62.46	7.243%	$66.984	$66.98	$67.00	$67.00
Purchase #2	$105.57	5.554%	$111.4334	$111.43	$111.45	$111.40
Purchase #3	$135.27	6.321%	$143.8204	$143.82	$143.80	$143.80
Purchase #4	$206.69	10.466%	$228.3222	$228.32	$228.30	$228.30
Purchase #5	$240.38	9.494%	$263.2017	$263.20	$263.20	$263.20
Purchase #6	$220.74	12.146%	$247.5511	$247.55	$247.55	$247.60
Purchase #7	$53.56	10.653%	$59.2657	$59.27	$59.25	$59.30
7 purchase totals =	$1,024.67		$1,120.5785	$1,120.57	$1,120.55	$1,120.60