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	$44.52	5.747%	$47.0786	$47.08	$47.10	$47.10
Purchase #2	$51.34	4.421%	$53.6097	$53.61	$53.60	$53.60
Purchase #3	$6.64	13.286%	$7.5222	$7.52	$7.50	$7.50
Purchase #4	$82.47	11.729%	$92.1429	$92.14	$92.15	$92.10
Purchase #5	$157.62	8.700%	$171.3329	$171.33	$171.35	$171.30
Purchase #6	$82.75	3.123%	$85.3343	$85.33	$85.35	$85.30
Purchase #7	$56.47	12.465%	$63.509	$63.51	$63.50	$63.50
7 purchase totals =	$481.81		$520.5296	$520.52	$520.55	$520.40