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	$30.78	8.668%	$33.448	$33.45	$33.45	$33.40
Purchase #2	$67.76	11.316%	$75.4277	$75.43	$75.45	$75.40
Purchase #3	$241.25	8.428%	$261.5826	$261.58	$261.60	$261.60
Purchase #4	$186.81	11.476%	$208.2483	$208.25	$208.25	$208.20
Purchase #5	$181.66	8.325%	$196.7832	$196.78	$196.80	$196.80
Purchase #6	$208.70	10.216%	$230.0208	$230.02	$230.00	$230.00
Purchase #7	$131.64	10.178%	$145.0383	$145.04	$145.05	$145.00
7 purchase totals =	$1,048.60		$1,150.5489	$1,150.55	$1,150.60	$1,150.40