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	$154.83	12.817%	$174.6746	$174.67	$174.65	$174.70
Purchase #2	$245.66	12.476%	$276.3085	$276.31	$276.30	$276.30
Purchase #3	$91.64	9.827%	$100.6455	$100.65	$100.65	$100.60
Purchase #4	$102.27	11.614%	$114.1476	$114.15	$114.15	$114.10
Purchase #5	$150.38	9.150%	$164.1398	$164.14	$164.15	$164.10
Purchase #6	$157.28	6.858%	$168.0663	$168.07	$168.05	$168.10
Purchase #7	$247.37	3.123%	$255.0954	$255.10	$255.10	$255.10
7 purchase totals =	$1,149.43		$1,253.0777	$1,253.09	$1,253.05	$1,253.00