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	$210.60	3.392%	$217.7436	$217.74	$217.75	$217.70
Purchase #2	$114.32	13.730%	$130.0161	$130.02	$130.00	$130.00
Purchase #3	$94.43	11.826%	$105.5973	$105.60	$105.60	$105.60
Purchase #4	$84.73	4.387%	$88.4471	$88.45	$88.45	$88.40
Purchase #5	$38.43	10.261%	$42.3733	$42.37	$42.35	$42.40
Purchase #6	$234.80	11.696%	$262.2622	$262.26	$262.25	$262.30
Purchase #7	$135.28	4.273%	$141.0605	$141.06	$141.05	$141.10
7 purchase totals =	$912.59		$987.5001	$987.50	$987.45	$987.50