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	$219.67	6.461%	$233.8629	$233.86	$233.85	$233.90
Purchase #2	$192.68	9.555%	$211.0906	$211.09	$211.10	$211.10
Purchase #3	$87.92	10.216%	$96.9019	$96.90	$96.90	$96.90
Purchase #4	$45.73	8.636%	$49.6792	$49.68	$49.70	$49.70
Purchase #5	$247.88	10.690%	$274.3784	$274.38	$274.40	$274.40
Purchase #6	$41.76	11.608%	$46.6075	$46.61	$46.60	$46.60
Purchase #7	$227.97	12.697%	$256.9154	$256.92	$256.90	$256.90
7 purchase totals =	$1,063.61		$1,169.4359	$1,169.44	$1,169.45	$1,169.50