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	$226.79	13.278%	$256.9032	$256.90	$256.90	$256.90
Purchase #2	$59.35	5.650%	$62.7033	$62.70	$62.70	$62.70
Purchase #3	$83.66	11.536%	$93.311	$93.31	$93.30	$93.30
Purchase #4	$212.46	3.607%	$220.1234	$220.12	$220.10	$220.10
Purchase #5	$179.95	9.329%	$196.7375	$196.74	$196.75	$196.70
Purchase #6	$18.40	11.631%	$20.5401	$20.54	$20.55	$20.50
Purchase #7	$142.99	12.757%	$161.2312	$161.23	$161.25	$161.20
7 purchase totals =	$923.60		$1,011.5497	$1,011.54	$1,011.55	$1,011.40