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	$53.99	9.603%	$59.1747	$59.17	$59.15	$59.20
Purchase #2	$17.82	3.324%	$18.4123	$18.41	$18.40	$18.40
Purchase #3	$145.73	10.648%	$161.2473	$161.25	$161.25	$161.20
Purchase #4	$127.32	3.256%	$131.4655	$131.47	$131.45	$131.50
Purchase #5	$80.37	11.135%	$89.3192	$89.32	$89.30	$89.30
Purchase #6	$168.29	11.468%	$187.5895	$187.59	$187.60	$187.60
Purchase #7	$52.83	3.300%	$54.5734	$54.57	$54.55	$54.60
7 purchase totals =	$646.35		$701.7819	$701.78	$701.70	$701.80