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	$161.81	12.510%	$182.0524	$182.05	$182.05	$182.10
Purchase #2	$95.59	4.834%	$100.2108	$100.21	$100.20	$100.20
Purchase #3	$156.37	9.573%	$171.3393	$171.34	$171.35	$171.30
Purchase #4	$17.51	5.246%	$18.4286	$18.43	$18.45	$18.40
Purchase #5	$33.90	12.612%	$38.1755	$38.18	$38.20	$38.20
Purchase #6	$61.39	7.723%	$66.1311	$66.13	$66.15	$66.10
Purchase #7	$240.72	10.278%	$265.4612	$265.46	$265.45	$265.50
7 purchase totals =	$767.29		$841.7989	$841.80	$841.85	$841.80