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	$72.39	9.390%	$79.1874	$79.19	$79.20	$79.20
Purchase #2	$92.37	8.205%	$99.949	$99.95	$99.95	$99.90
Purchase #3	$35.55	7.335%	$38.1576	$38.16	$38.15	$38.20
Purchase #4	$68.81	5.428%	$72.545	$72.55	$72.55	$72.50
Purchase #5	$26.36	9.614%	$28.8943	$28.89	$28.90	$28.90
Purchase #6	$250.60	12.768%	$282.5966	$282.60	$282.60	$282.60
Purchase #7	$176.43	6.237%	$187.4339	$187.43	$187.45	$187.40
7 purchase totals =	$722.51		$788.7638	$788.77	$788.80	$788.70