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	$208.25	6.803%	$222.4172	$222.42	$222.40	$222.40
Purchase #2	$32.41	8.787%	$35.2579	$35.26	$35.25	$35.30
Purchase #3	$31.29	7.743%	$33.7128	$33.71	$33.70	$33.70
Purchase #4	$28.95	9.219%	$31.6189	$31.62	$31.60	$31.60
Purchase #5	$156.64	3.690%	$162.42	$162.42	$162.40	$162.40
Purchase #6	$115.50	13.611%	$131.2207	$131.22	$131.20	$131.20
Purchase #7	$95.39	6.396%	$101.4911	$101.49	$101.50	$101.50
7 purchase totals =	$668.43		$718.1386	$718.14	$718.05	$718.10