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	$139.79	9.149%	$152.5794	$152.58	$152.60	$152.60
Purchase #2	$161.91	3.611%	$167.7566	$167.76	$167.75	$167.80
Purchase #3	$128.29	3.770%	$133.1265	$133.13	$133.15	$133.10
Purchase #4	$119.54	13.818%	$136.058	$136.06	$136.05	$136.10
Purchase #5	$89.59	6.608%	$95.5101	$95.51	$95.50	$95.50
Purchase #6	$247.34	13.427%	$280.5503	$280.55	$280.55	$280.60
Purchase #7	$86.48	9.660%	$94.834	$94.83	$94.85	$94.80
7 purchase totals =	$972.94		$1,060.4149	$1,060.42	$1,060.45	$1,060.50