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	$163.83	5.444%	$172.7489	$172.75	$172.75	$172.70
Purchase #2	$68.96	13.727%	$78.4261	$78.43	$78.45	$78.40
Purchase #3	$90.94	5.221%	$95.688	$95.69	$95.70	$95.70
Purchase #4	$44.66	12.204%	$50.1103	$50.11	$50.10	$50.10
Purchase #5	$88.51	13.840%	$100.7598	$100.76	$100.75	$100.80
Purchase #6	$176.47	4.844%	$185.0182	$185.02	$185.00	$185.00
Purchase #7	$83.76	6.730%	$89.397	$89.40	$89.40	$89.40
7 purchase totals =	$717.13		$772.1483	$772.16	$772.15	$772.10