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	$94.61	9.560%	$103.6547	$103.65	$103.65	$103.70
Purchase #2	$86.83	6.240%	$92.2482	$92.25	$92.25	$92.20
Purchase #3	$118.61	4.116%	$123.492	$123.49	$123.50	$123.50
Purchase #4	$91.57	12.744%	$103.2397	$103.24	$103.25	$103.20
Purchase #5	$27.80	7.589%	$29.9097	$29.91	$29.90	$29.90
Purchase #6	$127.45	10.364%	$140.6589	$140.66	$140.65	$140.70
Purchase #7	$87.89	3.183%	$90.6875	$90.69	$90.70	$90.70
7 purchase totals =	$634.76		$683.8907	$683.89	$683.90	$683.90