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	$238.74	6.659%	$254.6377	$254.64	$254.65	$254.60
Purchase #2	$192.40	4.161%	$200.4058	$200.41	$200.40	$200.40
Purchase #3	$61.47	8.506%	$66.6986	$66.70	$66.70	$66.70
Purchase #4	$131.54	8.443%	$142.6459	$142.65	$142.65	$142.60
Purchase #5	$96.49	3.166%	$99.5449	$99.54	$99.55	$99.50
Purchase #6	$119.93	11.772%	$134.0482	$134.05	$134.05	$134.00
Purchase #7	$198.46	4.630%	$207.6487	$207.65	$207.65	$207.60
7 purchase totals =	$1,039.03		$1,105.6298	$1,105.64	$1,105.65	$1,105.40