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	$144.40	10.786%	$159.975	$159.98	$160.00	$160.00
Purchase #2	$175.33	5.850%	$185.5868	$185.59	$185.60	$185.60
Purchase #3	$204.53	13.598%	$232.342	$232.34	$232.35	$232.30
Purchase #4	$248.58	4.264%	$259.1795	$259.18	$259.20	$259.20
Purchase #5	$98.67	10.240%	$108.7738	$108.77	$108.75	$108.80
Purchase #6	$64.65	11.513%	$72.0932	$72.09	$72.10	$72.10
Purchase #7	$162.43	3.769%	$168.552	$168.55	$168.55	$168.60
7 purchase totals =	$1,098.59		$1,186.5023	$1,186.50	$1,186.55	$1,186.60