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	$230.48	5.685%	$243.5828	$243.58	$243.60	$243.60
Purchase #2	$168.77	9.286%	$184.442	$184.44	$184.45	$184.40
Purchase #3	$245.34	11.603%	$273.8068	$273.81	$273.80	$273.80
Purchase #4	$134.31	11.241%	$149.4078	$149.41	$149.40	$149.40
Purchase #5	$231.62	13.782%	$263.5419	$263.54	$263.55	$263.50
Purchase #6	$130.64	5.126%	$137.3366	$137.34	$137.35	$137.30
Purchase #7	$137.38	11.291%	$152.8916	$152.89	$152.90	$152.90
7 purchase totals =	$1,278.54		$1,405.0095	$1,405.01	$1,405.05	$1,404.90