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	$59.25	3.579%	$61.3706	$61.37	$61.35	$61.40
Purchase #2	$131.43	10.668%	$145.451	$145.45	$145.45	$145.50
Purchase #3	$99.82	11.287%	$111.0867	$111.09	$111.10	$111.10
Purchase #4	$36.90	6.374%	$39.252	$39.25	$39.25	$39.30
Purchase #5	$187.51	8.647%	$203.724	$203.72	$203.70	$203.70
Purchase #6	$74.32	9.438%	$81.3343	$81.33	$81.35	$81.30
Purchase #7	$233.98	10.572%	$258.7164	$258.72	$258.70	$258.70
7 purchase totals =	$823.21		$900.9350	$900.93	$900.90	$901.00