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	$100.43	11.360%	$111.8388	$111.84	$111.85	$111.80
Purchase #2	$206.57	3.206%	$213.1926	$213.19	$213.20	$213.20
Purchase #3	$30.54	10.298%	$33.685	$33.69	$33.70	$33.70
Purchase #4	$149.88	9.753%	$164.4978	$164.50	$164.50	$164.50
Purchase #5	$32.69	4.164%	$34.0512	$34.05	$34.05	$34.10
Purchase #6	$161.81	10.121%	$178.1868	$178.19	$178.20	$178.20
Purchase #7	$16.74	12.492%	$18.8312	$18.83	$18.85	$18.80
7 purchase totals =	$698.66		$754.2834	$754.29	$754.35	$754.30