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	$5.52	6.598%	$5.8842	$5.88	$5.90	$5.90
Purchase #2	$33.45	6.379%	$35.5838	$35.58	$35.60	$35.60
Purchase #3	$82.84	7.867%	$89.357	$89.36	$89.35	$89.40
Purchase #4	$209.54	11.388%	$233.4024	$233.40	$233.40	$233.40
Purchase #5	$61.95	6.143%	$65.7556	$65.76	$65.75	$65.80
Purchase #6	$75.50	8.613%	$82.0028	$82.00	$82.00	$82.00
Purchase #7	$219.52	10.164%	$241.832	$241.83	$241.85	$241.80
7 purchase totals =	$688.32		$753.8178	$753.81	$753.85	$753.90