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	$65.64	9.741%	$72.034	$72.03	$72.05	$72.00
Purchase #2	$81.90	8.676%	$89.0056	$89.01	$89.00	$89.00
Purchase #3	$69.91	4.274%	$72.898	$72.90	$72.90	$72.90
Purchase #4	$147.76	10.591%	$163.4093	$163.41	$163.40	$163.40
Purchase #5	$89.35	5.566%	$94.3232	$94.32	$94.30	$94.30
Purchase #6	$209.80	4.608%	$219.4676	$219.47	$219.45	$219.50
Purchase #7	$14.63	8.691%	$15.9015	$15.90	$15.90	$15.90
7 purchase totals =	$678.99		$727.0392	$727.04	$727.00	$727.00