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	$249.97	5.153%	$262.851	$262.85	$262.85	$262.90
Purchase #2	$105.92	3.551%	$109.6812	$109.68	$109.70	$109.70
Purchase #3	$188.74	10.674%	$208.8861	$208.89	$208.90	$208.90
Purchase #4	$135.52	12.465%	$152.4126	$152.41	$152.40	$152.40
Purchase #5	$192.31	13.153%	$217.6045	$217.60	$217.60	$217.60
Purchase #6	$150.74	3.334%	$155.7657	$155.77	$155.75	$155.80
Purchase #7	$17.89	11.214%	$19.8962	$19.90	$19.90	$19.90
7 purchase totals =	$1,041.09		$1,127.0973	$1,127.10	$1,127.10	$1,127.20