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	$62.44	7.874%	$67.3565	$67.36	$67.35	$67.40
Purchase #2	$229.52	6.710%	$244.9208	$244.92	$244.90	$244.90
Purchase #3	$178.29	10.279%	$196.6164	$196.62	$196.60	$196.60
Purchase #4	$39.74	8.769%	$43.2248	$43.22	$43.20	$43.20
Purchase #5	$226.94	5.707%	$239.8915	$239.89	$239.90	$239.90
Purchase #6	$156.93	12.184%	$176.0504	$176.05	$176.05	$176.10
Purchase #7	$89.36	4.780%	$93.6314	$93.63	$93.65	$93.60
7 purchase totals =	$983.22		$1,061.6918	$1,061.69	$1,061.65	$1,061.70