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	$154.71	5.160%	$162.693	$162.69	$162.70	$162.70
Purchase #2	$181.77	9.475%	$198.9927	$198.99	$199.00	$199.00
Purchase #3	$52.45	13.453%	$59.5061	$59.51	$59.50	$59.50
Purchase #4	$241.72	11.836%	$270.33	$270.33	$270.35	$270.30
Purchase #5	$173.38	8.117%	$187.4533	$187.45	$187.45	$187.50
Purchase #6	$109.82	11.357%	$122.2923	$122.29	$122.30	$122.30
Purchase #7	$24.63	10.516%	$27.2201	$27.22	$27.20	$27.20
7 purchase totals =	$938.48		$1,028.4875	$1,028.48	$1,028.50	$1,028.50