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	$77.83	11.556%	$86.824	$86.82	$86.80	$86.80
Purchase #2	$129.54	10.111%	$142.6378	$142.64	$142.65	$142.60
Purchase #3	$237.74	9.736%	$260.8864	$260.89	$260.90	$260.90
Purchase #4	$225.43	12.866%	$254.4338	$254.43	$254.45	$254.40
Purchase #5	$130.31	10.326%	$143.7658	$143.77	$143.75	$143.80
Purchase #6	$143.44	8.602%	$155.7787	$155.78	$155.80	$155.80
Purchase #7	$41.59	4.154%	$43.3176	$43.32	$43.30	$43.30
7 purchase totals =	$985.88		$1,087.6441	$1,087.65	$1,087.65	$1,087.60