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	$126.80	9.848%	$139.2873	$139.29	$139.30	$139.30
Purchase #2	$233.53	4.507%	$244.0552	$244.06	$244.05	$244.10
Purchase #3	$160.76	3.192%	$165.8915	$165.89	$165.90	$165.90
Purchase #4	$86.59	8.496%	$93.9467	$93.95	$93.95	$93.90
Purchase #5	$48.49	10.656%	$53.6571	$53.66	$53.65	$53.70
Purchase #6	$179.82	6.108%	$190.8034	$190.80	$190.80	$190.80
Purchase #7	$116.93	12.718%	$131.8012	$131.80	$131.80	$131.80
7 purchase totals =	$952.92		$1,019.4424	$1,019.45	$1,019.45	$1,019.50