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	$42.94	4.208%	$44.7469	$44.75	$44.75	$44.70
Purchase #2	$81.27	5.789%	$85.9747	$85.97	$85.95	$86.00
Purchase #3	$109.45	12.504%	$123.1356	$123.14	$123.15	$123.10
Purchase #4	$113.50	4.235%	$118.3067	$118.31	$118.30	$118.30
Purchase #5	$166.52	6.830%	$177.8933	$177.89	$177.90	$177.90
Purchase #6	$9.66	6.809%	$10.3177	$10.32	$10.30	$10.30
Purchase #7	$239.98	6.729%	$256.1283	$256.13	$256.15	$256.10
7 purchase totals =	$763.32		$816.5032	$816.51	$816.50	$816.40