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	$130.40	10.326%	$143.8651	$143.87	$143.85	$143.90
Purchase #2	$67.65	6.336%	$71.9363	$71.94	$71.95	$71.90
Purchase #3	$62.28	12.132%	$69.8358	$69.84	$69.85	$69.80
Purchase #4	$10.29	11.227%	$11.4453	$11.45	$11.45	$11.40
Purchase #5	$105.66	5.294%	$111.2536	$111.25	$111.25	$111.30
Purchase #6	$95.60	7.872%	$103.1256	$103.13	$103.15	$103.10
Purchase #7	$196.36	5.180%	$206.5314	$206.53	$206.55	$206.50
7 purchase totals =	$668.24		$717.9931	$718.01	$718.05	$717.90