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	$246.75	3.554%	$255.5195	$255.52	$255.50	$255.50
Purchase #2	$39.84	6.276%	$42.3404	$42.34	$42.35	$42.30
Purchase #3	$157.47	6.420%	$167.5796	$167.58	$167.60	$167.60
Purchase #4	$248.82	13.636%	$282.7491	$282.75	$282.75	$282.70
Purchase #5	$53.95	13.223%	$61.0838	$61.08	$61.10	$61.10
Purchase #6	$197.34	5.464%	$208.1227	$208.12	$208.10	$208.10
Purchase #7	$83.76	3.247%	$86.4797	$86.48	$86.50	$86.50
7 purchase totals =	$1,027.93		$1,103.8748	$1,103.87	$1,103.90	$1,103.80