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	$24.25	5.557%	$25.5976	$25.60	$25.60	$25.60
Purchase #2	$127.85	7.831%	$137.8619	$137.86	$137.85	$137.90
Purchase #3	$143.90	8.480%	$156.1027	$156.10	$156.10	$156.10
Purchase #4	$71.27	6.452%	$75.8683	$75.87	$75.85	$75.90
Purchase #5	$17.50	13.390%	$19.8433	$19.84	$19.85	$19.80
Purchase #6	$101.88	3.288%	$105.2298	$105.23	$105.25	$105.20
Purchase #7	$14.68	3.736%	$15.2284	$15.23	$15.25	$15.20
7 purchase totals =	$501.33		$535.7320	$535.73	$535.75	$535.70