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	$194.31	13.433%	$220.4117	$220.41	$220.40	$220.40
Purchase #2	$34.64	8.535%	$37.5965	$37.60	$37.60	$37.60
Purchase #3	$148.65	3.603%	$154.0059	$154.01	$154.00	$154.00
Purchase #4	$180.82	8.128%	$195.517	$195.52	$195.50	$195.50
Purchase #5	$96.60	9.558%	$105.833	$105.83	$105.85	$105.80
Purchase #6	$16.68	11.375%	$18.5774	$18.58	$18.60	$18.60
Purchase #7	$53.69	3.581%	$55.6126	$55.61	$55.60	$55.60
7 purchase totals =	$725.39		$787.5541	$787.56	$787.55	$787.50