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	$47.60	13.304%	$53.9327	$53.93	$53.95	$53.90
Purchase #2	$187.80	4.810%	$196.8332	$196.83	$196.85	$196.80
Purchase #3	$64.54	9.232%	$70.4983	$70.50	$70.50	$70.50
Purchase #4	$209.64	4.143%	$218.3254	$218.33	$218.35	$218.30
Purchase #5	$126.65	8.855%	$137.8649	$137.86	$137.85	$137.90
Purchase #6	$182.50	9.651%	$200.1131	$200.11	$200.10	$200.10
Purchase #7	$71.77	12.758%	$80.9264	$80.93	$80.95	$80.90
7 purchase totals =	$890.50		$958.4940	$958.49	$958.55	$958.40