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	$129.61	5.291%	$136.4677	$136.47	$136.45	$136.50
Purchase #2	$175.48	6.269%	$186.4808	$186.48	$186.50	$186.50
Purchase #3	$242.97	4.834%	$254.7152	$254.72	$254.70	$254.70
Purchase #4	$138.88	12.145%	$155.747	$155.75	$155.75	$155.70
Purchase #5	$180.59	10.549%	$199.6404	$199.64	$199.65	$199.60
Purchase #6	$154.50	5.164%	$162.4784	$162.48	$162.50	$162.50
Purchase #7	$169.82	12.747%	$191.467	$191.47	$191.45	$191.50
7 purchase totals =	$1,191.85		$1,286.9965	$1,287.01	$1,287.00	$1,287.00