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	$65.73	9.583%	$72.0289	$72.03	$72.05	$72.00
Purchase #2	$29.36	8.528%	$31.8638	$31.86	$31.85	$31.90
Purchase #3	$206.80	11.196%	$229.9533	$229.95	$229.95	$230.00
Purchase #4	$196.29	8.522%	$213.0178	$213.02	$213.00	$213.00
Purchase #5	$49.38	8.341%	$53.4988	$53.50	$53.50	$53.50
Purchase #6	$233.91	10.840%	$259.2658	$259.27	$259.25	$259.30
Purchase #7	$138.92	3.640%	$143.9767	$143.98	$144.00	$144.00
7 purchase totals =	$920.39		$1,003.6051	$1,003.61	$1,003.60	$1,003.70