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	$84.85	11.843%	$94.8988	$94.90	$94.90	$94.90
Purchase #2	$63.83	11.804%	$71.3645	$71.36	$71.35	$71.40
Purchase #3	$72.96	8.119%	$78.8836	$78.88	$78.90	$78.90
Purchase #4	$141.39	6.509%	$150.5931	$150.59	$150.60	$150.60
Purchase #5	$153.64	13.227%	$173.962	$173.96	$173.95	$174.00
Purchase #6	$49.40	5.289%	$52.0128	$52.01	$52.00	$52.00
Purchase #7	$250.43	9.852%	$275.1024	$275.10	$275.10	$275.10
7 purchase totals =	$816.50		$896.8172	$896.80	$896.80	$896.90