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	$59.63	12.417%	$67.0343	$67.03	$67.05	$67.00
Purchase #2	$245.31	5.862%	$259.6901	$259.69	$259.70	$259.70
Purchase #3	$42.45	3.534%	$43.9502	$43.95	$43.95	$44.00
Purchase #4	$17.49	3.410%	$18.0864	$18.09	$18.10	$18.10
Purchase #5	$12.29	13.389%	$13.9355	$13.94	$13.95	$13.90
Purchase #6	$156.42	4.165%	$162.9349	$162.93	$162.95	$162.90
Purchase #7	$32.86	4.348%	$34.2888	$34.29	$34.30	$34.30
7 purchase totals =	$566.45		$599.9202	$599.92	$600.00	$599.90