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	$24.41	6.704%	$26.0464	$26.05	$26.05	$26.00
Purchase #2	$247.64	3.175%	$255.5026	$255.50	$255.50	$255.50
Purchase #3	$244.34	6.197%	$259.4817	$259.48	$259.50	$259.50
Purchase #4	$137.50	7.768%	$148.181	$148.18	$148.20	$148.20
Purchase #5	$137.62	3.440%	$142.3541	$142.35	$142.35	$142.40
Purchase #6	$170.85	8.438%	$185.2663	$185.27	$185.25	$185.30
Purchase #7	$56.53	10.762%	$62.6138	$62.61	$62.60	$62.60
7 purchase totals =	$1,018.89		$1,079.4459	$1,079.44	$1,079.45	$1,079.50