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	$162.64	11.842%	$181.8998	$181.90	$181.90	$181.90
Purchase #2	$136.82	6.352%	$145.5108	$145.51	$145.50	$145.50
Purchase #3	$138.63	11.297%	$154.291	$154.29	$154.30	$154.30
Purchase #4	$229.94	12.368%	$258.379	$258.38	$258.40	$258.40
Purchase #5	$32.91	3.511%	$34.0655	$34.07	$34.05	$34.10
Purchase #6	$96.89	3.591%	$100.3693	$100.37	$100.35	$100.40
Purchase #7	$121.81	8.305%	$131.9263	$131.93	$131.95	$131.90
7 purchase totals =	$919.64		$1,006.4417	$1,006.45	$1,006.45	$1,006.50