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	$87.53	3.745%	$90.808	$90.81	$90.80	$90.80
Purchase #2	$153.37	3.220%	$158.3085	$158.31	$158.30	$158.30
Purchase #3	$198.63	13.566%	$225.5761	$225.58	$225.60	$225.60
Purchase #4	$63.79	12.530%	$71.7829	$71.78	$71.80	$71.80
Purchase #5	$179.44	11.675%	$200.3896	$200.39	$200.40	$200.40
Purchase #6	$147.75	8.580%	$160.427	$160.43	$160.45	$160.40
Purchase #7	$197.99	6.191%	$210.2476	$210.25	$210.25	$210.20
7 purchase totals =	$1,028.50		$1,117.5397	$1,117.55	$1,117.60	$1,117.50