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	$231.38	11.134%	$257.1418	$257.14	$257.15	$257.10
Purchase #2	$11.29	3.499%	$11.685	$11.69	$11.70	$11.70
Purchase #3	$90.51	10.159%	$99.7049	$99.70	$99.70	$99.70
Purchase #4	$72.89	13.426%	$82.6762	$82.68	$82.70	$82.70
Purchase #5	$45.30	9.852%	$49.763	$49.76	$49.75	$49.80
Purchase #6	$28.65	13.476%	$32.5109	$32.51	$32.50	$32.50
Purchase #7	$234.79	6.841%	$250.852	$250.85	$250.85	$250.90
7 purchase totals =	$714.81		$784.3338	$784.33	$784.35	$784.40