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	$208.59	6.832%	$222.8409	$222.84	$222.85	$222.80
Purchase #2	$87.89	5.446%	$92.6765	$92.68	$92.70	$92.70
Purchase #3	$26.75	11.788%	$29.9033	$29.90	$29.90	$29.90
Purchase #4	$222.48	11.655%	$248.41	$248.41	$248.40	$248.40
Purchase #5	$75.58	3.371%	$78.1278	$78.13	$78.15	$78.10
Purchase #6	$68.31	7.735%	$73.5938	$73.59	$73.60	$73.60
Purchase #7	$65.44	12.138%	$73.3831	$73.38	$73.40	$73.40
7 purchase totals =	$755.04		$818.9354	$818.93	$819.00	$818.90