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	$166.76	11.419%	$185.8023	$185.80	$185.80	$185.80
Purchase #2	$6.79	8.586%	$7.373	$7.37	$7.35	$7.40
Purchase #3	$50.59	8.548%	$54.9144	$54.91	$54.90	$54.90
Purchase #4	$127.58	13.556%	$144.8747	$144.87	$144.85	$144.90
Purchase #5	$120.81	13.726%	$137.3924	$137.39	$137.40	$137.40
Purchase #6	$78.39	6.759%	$83.6884	$83.69	$83.70	$83.70
Purchase #7	$186.34	8.335%	$201.8714	$201.87	$201.85	$201.90
7 purchase totals =	$737.26		$815.9166	$815.90	$815.85	$816.00