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	$68.32	3.392%	$70.6374	$70.64	$70.65	$70.60
Purchase #2	$14.95	7.837%	$16.1216	$16.12	$16.10	$16.10
Purchase #3	$97.40	12.473%	$109.5487	$109.55	$109.55	$109.50
Purchase #4	$43.55	9.278%	$47.5906	$47.59	$47.60	$47.60
Purchase #5	$101.57	3.743%	$105.3718	$105.37	$105.35	$105.40
Purchase #6	$175.72	13.327%	$199.1382	$199.14	$199.15	$199.10
Purchase #7	$102.55	3.154%	$105.7844	$105.78	$105.80	$105.80
7 purchase totals =	$604.06		$654.1927	$654.19	$654.20	$654.10