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	$231.50	10.592%	$256.0205	$256.02	$256.00	$256.00
Purchase #2	$114.98	13.573%	$130.5862	$130.59	$130.60	$130.60
Purchase #3	$234.42	13.269%	$265.5252	$265.53	$265.55	$265.50
Purchase #4	$245.94	12.641%	$277.0293	$277.03	$277.05	$277.00
Purchase #5	$56.71	13.474%	$64.3511	$64.35	$64.35	$64.40
Purchase #6	$13.60	9.484%	$14.8898	$14.89	$14.90	$14.90
Purchase #7	$91.28	10.417%	$100.7886	$100.79	$100.80	$100.80
7 purchase totals =	$988.43		$1,109.1907	$1,109.20	$1,109.25	$1,109.20