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	$188.72	3.113%	$194.5949	$194.59	$194.60	$194.60
Purchase #2	$225.81	12.286%	$253.553	$253.55	$253.55	$253.60
Purchase #3	$11.43	12.771%	$12.8897	$12.89	$12.90	$12.90
Purchase #4	$93.47	9.682%	$102.5198	$102.52	$102.50	$102.50
Purchase #5	$48.28	10.526%	$53.362	$53.36	$53.35	$53.40
Purchase #6	$90.86	9.603%	$99.5853	$99.59	$99.60	$99.60
Purchase #7	$8.82	6.513%	$9.3944	$9.39	$9.40	$9.40
7 purchase totals =	$667.39		$725.8991	$725.89	$725.90	$726.00