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	$33.37	6.398%	$35.505	$35.51	$35.50	$35.50
Purchase #2	$243.90	5.196%	$256.573	$256.57	$256.55	$256.60
Purchase #3	$14.50	8.660%	$15.7557	$15.76	$15.75	$15.80
Purchase #4	$58.34	10.427%	$64.4231	$64.42	$64.40	$64.40
Purchase #5	$45.47	4.856%	$47.678	$47.68	$47.70	$47.70
Purchase #6	$33.57	13.630%	$38.1456	$38.15	$38.15	$38.10
Purchase #7	$69.25	7.543%	$74.4735	$74.47	$74.45	$74.50
7 purchase totals =	$498.40		$532.5539	$532.56	$532.50	$532.60