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	$47.82	11.730%	$53.4293	$53.43	$53.45	$53.40
Purchase #2	$200.76	6.181%	$213.169	$213.17	$213.15	$213.20
Purchase #3	$121.57	13.450%	$137.9212	$137.92	$137.90	$137.90
Purchase #4	$70.99	10.549%	$78.4787	$78.48	$78.50	$78.50
Purchase #5	$232.43	12.631%	$261.7882	$261.79	$261.80	$261.80
Purchase #6	$167.87	10.482%	$185.4661	$185.47	$185.45	$185.50
Purchase #7	$109.95	9.636%	$120.5448	$120.54	$120.55	$120.50
7 purchase totals =	$951.39		$1,050.7973	$1,050.80	$1,050.80	$1,050.80