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	$220.31	6.443%	$234.5046	$234.50	$234.50	$234.50
Purchase #2	$190.70	7.442%	$204.8919	$204.89	$204.90	$204.90
Purchase #3	$33.97	3.244%	$35.072	$35.07	$35.05	$35.10
Purchase #4	$21.59	13.642%	$24.5353	$24.54	$24.55	$24.50
Purchase #5	$164.76	5.704%	$174.1579	$174.16	$174.15	$174.20
Purchase #6	$133.33	6.858%	$142.4738	$142.47	$142.45	$142.50
Purchase #7	$239.93	7.605%	$258.1767	$258.18	$258.20	$258.20
7 purchase totals =	$1,004.59		$1,073.8122	$1,073.81	$1,073.80	$1,073.90