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	$155.86	5.746%	$164.8157	$164.82	$164.80	$164.80
Purchase #2	$52.79	12.373%	$59.3217	$59.32	$59.30	$59.30
Purchase #3	$214.60	12.592%	$241.6224	$241.62	$241.60	$241.60
Purchase #4	$31.85	4.394%	$33.2495	$33.25	$33.25	$33.20
Purchase #5	$106.80	11.736%	$119.334	$119.33	$119.35	$119.30
Purchase #6	$156.41	9.219%	$170.8294	$170.83	$170.85	$170.80
Purchase #7	$242.93	6.225%	$258.0524	$258.05	$258.05	$258.10
7 purchase totals =	$961.24		$1,047.2251	$1,047.22	$1,047.20	$1,047.10