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	$105.89	5.355%	$111.5604	$111.56	$111.55	$111.60
Purchase #2	$118.68	12.510%	$133.5269	$133.53	$133.55	$133.50
Purchase #3	$178.34	12.113%	$199.9423	$199.94	$199.95	$199.90
Purchase #4	$243.52	4.804%	$255.2187	$255.22	$255.20	$255.20
Purchase #5	$188.63	9.795%	$207.1063	$207.11	$207.10	$207.10
Purchase #6	$9.73	7.661%	$10.4754	$10.48	$10.50	$10.50
Purchase #7	$18.25	6.202%	$19.3819	$19.38	$19.40	$19.40
7 purchase totals =	$863.04		$937.2119	$937.22	$937.25	$937.20