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	$82.25	6.838%	$87.8743	$87.87	$87.85	$87.90
Purchase #2	$231.32	11.367%	$257.6141	$257.61	$257.60	$257.60
Purchase #3	$28.72	7.606%	$30.9044	$30.90	$30.90	$30.90
Purchase #4	$121.30	5.464%	$127.9278	$127.93	$127.95	$127.90
Purchase #5	$106.33	4.500%	$111.1149	$111.11	$111.10	$111.10
Purchase #6	$137.79	7.590%	$148.2483	$148.25	$148.25	$148.20
Purchase #7	$177.63	4.369%	$185.3907	$185.39	$185.40	$185.40
7 purchase totals =	$885.34		$949.0745	$949.06	$949.05	$949.00