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	$14.55	7.293%	$15.6111	$15.61	$15.60	$15.60
Purchase #2	$53.46	5.785%	$56.5527	$56.55	$56.55	$56.60
Purchase #3	$64.99	11.489%	$72.4567	$72.46	$72.45	$72.50
Purchase #4	$124.28	13.371%	$140.8975	$140.90	$140.90	$140.90
Purchase #5	$247.85	13.753%	$281.9368	$281.94	$281.95	$281.90
Purchase #6	$86.72	5.402%	$91.4046	$91.40	$91.40	$91.40
Purchase #7	$139.27	10.242%	$153.534	$153.53	$153.55	$153.50
7 purchase totals =	$731.12		$812.3934	$812.39	$812.40	$812.40