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	$228.48	9.598%	$250.4095	$250.41	$250.40	$250.40
Purchase #2	$50.48	8.757%	$54.9005	$54.90	$54.90	$54.90
Purchase #3	$11.48	10.564%	$12.6927	$12.69	$12.70	$12.70
Purchase #4	$234.88	12.204%	$263.5448	$263.54	$263.55	$263.50
Purchase #5	$32.34	9.422%	$35.3871	$35.39	$35.40	$35.40
Purchase #6	$192.92	13.206%	$218.397	$218.40	$218.40	$218.40
Purchase #7	$184.44	7.623%	$198.4999	$198.50	$198.50	$198.50
7 purchase totals =	$935.02		$1,033.8315	$1,033.83	$1,033.85	$1,033.80