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	$163.64	5.662%	$172.9053	$172.91	$172.90	$172.90
Purchase #2	$181.63	5.828%	$192.2154	$192.22	$192.20	$192.20
Purchase #3	$249.53	5.354%	$262.8898	$262.89	$262.90	$262.90
Purchase #4	$86.29	4.523%	$90.1929	$90.19	$90.20	$90.20
Purchase #5	$53.88	11.645%	$60.1543	$60.15	$60.15	$60.20
Purchase #6	$130.93	6.351%	$139.2454	$139.25	$139.25	$139.20
Purchase #7	$180.98	3.579%	$187.4573	$187.46	$187.45	$187.50
7 purchase totals =	$1,046.88		$1,105.0604	$1,105.07	$1,105.05	$1,105.10