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	$62.59	5.462%	$66.0087	$66.01	$66.00	$66.00
Purchase #2	$91.61	8.285%	$99.1999	$99.20	$99.20	$99.20
Purchase #3	$13.70	3.506%	$14.1803	$14.18	$14.20	$14.20
Purchase #4	$12.32	8.593%	$13.3787	$13.38	$13.40	$13.40
Purchase #5	$217.71	10.838%	$241.3054	$241.31	$241.30	$241.30
Purchase #6	$233.52	13.191%	$264.3236	$264.32	$264.30	$264.30
Purchase #7	$232.95	7.517%	$250.4609	$250.46	$250.45	$250.50
7 purchase totals =	$864.40		$948.8575	$948.86	$948.85	$948.90