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	$85.48	11.253%	$95.0991	$95.10	$95.10	$95.10
Purchase #2	$114.26	11.247%	$127.1108	$127.11	$127.10	$127.10
Purchase #3	$228.97	4.141%	$238.4516	$238.45	$238.45	$238.50
Purchase #4	$156.44	11.633%	$174.6387	$174.64	$174.65	$174.60
Purchase #5	$198.78	7.666%	$214.0185	$214.02	$214.00	$214.00
Purchase #6	$190.71	3.115%	$196.6506	$196.65	$196.65	$196.70
Purchase #7	$171.58	4.712%	$179.6648	$179.66	$179.65	$179.70
7 purchase totals =	$1,146.22		$1,225.6341	$1,225.63	$1,225.60	$1,225.70