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	$32.63	5.777%	$34.515	$34.52	$34.50	$34.50
Purchase #2	$243.49	6.355%	$258.9638	$258.96	$258.95	$259.00
Purchase #3	$115.98	10.630%	$128.3087	$128.31	$128.30	$128.30
Purchase #4	$193.59	3.176%	$199.7384	$199.74	$199.75	$199.70
Purchase #5	$190.38	3.341%	$196.7406	$196.74	$196.75	$196.70
Purchase #6	$245.47	13.859%	$279.4897	$279.49	$279.50	$279.50
Purchase #7	$52.54	5.590%	$55.477	$55.48	$55.50	$55.50
7 purchase totals =	$1,074.08		$1,153.2332	$1,153.24	$1,153.25	$1,153.20