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	$230.52	8.377%	$249.8307	$249.83	$249.85	$249.80
Purchase #2	$208.42	5.227%	$219.3141	$219.31	$219.30	$219.30
Purchase #3	$86.54	11.853%	$96.7976	$96.80	$96.80	$96.80
Purchase #4	$245.75	6.766%	$262.3774	$262.38	$262.40	$262.40
Purchase #5	$29.72	5.427%	$31.3329	$31.33	$31.35	$31.30
Purchase #6	$171.96	12.264%	$193.0492	$193.05	$193.05	$193.00
Purchase #7	$104.50	6.511%	$111.304	$111.30	$111.30	$111.30
7 purchase totals =	$1,077.41		$1,164.0059	$1,164.00	$1,164.05	$1,163.90