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	$58.52	12.529%	$65.852	$65.85	$65.85	$65.90
Purchase #2	$110.57	8.446%	$119.9087	$119.91	$119.90	$119.90
Purchase #3	$43.94	7.532%	$47.2496	$47.25	$47.25	$47.20
Purchase #4	$9.82	9.834%	$10.7857	$10.79	$10.80	$10.80
Purchase #5	$143.98	5.209%	$151.4799	$151.48	$151.50	$151.50
Purchase #6	$213.82	8.259%	$231.4794	$231.48	$231.50	$231.50
Purchase #7	$151.65	4.608%	$158.638	$158.64	$158.65	$158.60
7 purchase totals =	$732.30		$785.3933	$785.40	$785.45	$785.40