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	$116.63	13.149%	$131.9657	$131.97	$131.95	$132.00
Purchase #2	$92.72	6.188%	$98.4575	$98.46	$98.45	$98.50
Purchase #3	$173.65	8.761%	$188.8635	$188.86	$188.85	$188.90
Purchase #4	$186.55	7.387%	$200.3304	$200.33	$200.35	$200.30
Purchase #5	$116.54	13.847%	$132.6773	$132.68	$132.70	$132.70
Purchase #6	$72.80	12.770%	$82.0966	$82.10	$82.10	$82.10
Purchase #7	$140.36	6.544%	$149.5452	$149.55	$149.55	$149.50
7 purchase totals =	$899.25		$983.9362	$983.95	$983.95	$984.00