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	$213.31	6.312%	$226.7741	$226.77	$226.75	$226.80
Purchase #2	$97.85	4.512%	$102.265	$102.27	$102.25	$102.30
Purchase #3	$81.89	9.607%	$89.7572	$89.76	$89.75	$89.80
Purchase #4	$55.95	6.560%	$59.6203	$59.62	$59.60	$59.60
Purchase #5	$56.89	6.212%	$60.424	$60.42	$60.40	$60.40
Purchase #6	$172.55	11.757%	$192.8367	$192.84	$192.85	$192.80
Purchase #7	$15.87	13.602%	$18.0286	$18.03	$18.05	$18.00
7 purchase totals =	$694.31		$749.7059	$749.71	$749.65	$749.70