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	$50.50	8.320%	$54.7016	$54.70	$54.70	$54.70
Purchase #2	$189.83	11.311%	$211.3017	$211.30	$211.30	$211.30
Purchase #3	$187.32	9.191%	$204.5366	$204.54	$204.55	$204.50
Purchase #4	$88.27	9.202%	$96.3926	$96.39	$96.40	$96.40
Purchase #5	$220.38	6.156%	$233.9466	$233.95	$233.95	$233.90
Purchase #6	$168.69	13.175%	$190.9149	$190.91	$190.90	$190.90
Purchase #7	$44.97	10.282%	$49.5938	$49.59	$49.60	$49.60
7 purchase totals =	$949.96		$1,041.3878	$1,041.38	$1,041.40	$1,041.30