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	$96.36	4.763%	$100.9496	$100.95	$100.95	$100.90
Purchase #2	$33.80	7.641%	$36.3827	$36.38	$36.40	$36.40
Purchase #3	$190.90	9.560%	$209.15	$209.15	$209.15	$209.20
Purchase #4	$199.60	4.385%	$208.3525	$208.35	$208.35	$208.40
Purchase #5	$221.83	5.233%	$233.4384	$233.44	$233.45	$233.40
Purchase #6	$106.51	9.795%	$116.9427	$116.94	$116.95	$116.90
Purchase #7	$24.55	12.600%	$27.6433	$27.64	$27.65	$27.60
7 purchase totals =	$873.55		$932.8592	$932.85	$932.90	$932.80