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	$124.79	13.114%	$141.155	$141.16	$141.15	$141.20
Purchase #2	$133.37	7.681%	$143.6141	$143.61	$143.60	$143.60
Purchase #3	$108.58	6.365%	$115.4911	$115.49	$115.50	$115.50
Purchase #4	$23.83	5.283%	$25.0889	$25.09	$25.10	$25.10
Purchase #5	$150.78	11.528%	$168.1619	$168.16	$168.15	$168.20
Purchase #6	$163.48	6.852%	$174.6816	$174.68	$174.70	$174.70
Purchase #7	$31.78	6.715%	$33.914	$33.91	$33.90	$33.90
7 purchase totals =	$736.61		$802.1066	$802.10	$802.10	$802.20