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	$200.37	11.330%	$223.0719	$223.07	$223.05	$223.10
Purchase #2	$50.61	7.844%	$54.5798	$54.58	$54.60	$54.60
Purchase #3	$80.77	10.690%	$89.4043	$89.40	$89.40	$89.40
Purchase #4	$164.73	11.569%	$183.7876	$183.79	$183.80	$183.80
Purchase #5	$60.39	12.499%	$67.9381	$67.94	$67.95	$67.90
Purchase #6	$181.58	6.410%	$193.2193	$193.22	$193.20	$193.20
Purchase #7	$180.39	13.717%	$205.1341	$205.13	$205.15	$205.10
7 purchase totals =	$918.84		$1,017.1351	$1,017.13	$1,017.15	$1,017.10