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	$212.51	13.840%	$241.9214	$241.92	$241.90	$241.90
Purchase #2	$86.39	10.291%	$95.2804	$95.28	$95.30	$95.30
Purchase #3	$142.44	7.631%	$153.3096	$153.31	$153.30	$153.30
Purchase #4	$149.68	5.241%	$157.5247	$157.52	$157.50	$157.50
Purchase #5	$225.62	4.107%	$234.8862	$234.89	$234.90	$234.90
Purchase #6	$178.54	4.119%	$185.8941	$185.89	$185.90	$185.90
Purchase #7	$39.91	13.384%	$45.2516	$45.25	$45.25	$45.30
7 purchase totals =	$1,035.09		$1,114.0680	$1,114.06	$1,114.05	$1,114.10