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	$154.39	9.485%	$169.0339	$169.03	$169.05	$169.00
Purchase #2	$205.65	9.874%	$225.9559	$225.96	$225.95	$226.00
Purchase #3	$172.45	10.383%	$190.3555	$190.36	$190.35	$190.40
Purchase #4	$94.70	5.462%	$99.8725	$99.87	$99.85	$99.90
Purchase #5	$237.92	13.382%	$269.7585	$269.76	$269.75	$269.80
Purchase #6	$156.78	4.670%	$164.1016	$164.10	$164.10	$164.10
Purchase #7	$95.27	4.265%	$99.3333	$99.33	$99.35	$99.30
7 purchase totals =	$1,117.16		$1,218.4112	$1,218.41	$1,218.40	$1,218.50