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	$112.88	8.684%	$122.6825	$122.68	$122.70	$122.70
Purchase #2	$166.55	13.730%	$189.4173	$189.42	$189.40	$189.40
Purchase #3	$151.67	3.256%	$156.6084	$156.61	$156.60	$156.60
Purchase #4	$117.66	8.428%	$127.5764	$127.58	$127.60	$127.60
Purchase #5	$20.50	4.473%	$21.417	$21.42	$21.40	$21.40
Purchase #6	$89.56	4.857%	$93.9099	$93.91	$93.90	$93.90
Purchase #7	$178.51	4.157%	$185.9307	$185.93	$185.95	$185.90
7 purchase totals =	$837.33		$897.5422	$897.55	$897.55	$897.50