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	$203.52	6.558%	$216.8668	$216.87	$216.85	$216.90
Purchase #2	$131.52	12.576%	$148.06	$148.06	$148.05	$148.10
Purchase #3	$146.53	13.556%	$166.3936	$166.39	$166.40	$166.40
Purchase #4	$147.76	13.176%	$167.2289	$167.23	$167.25	$167.20
Purchase #5	$153.56	9.633%	$168.3524	$168.35	$168.35	$168.40
Purchase #6	$67.84	5.298%	$71.4342	$71.43	$71.45	$71.40
Purchase #7	$68.57	13.369%	$77.7371	$77.74	$77.75	$77.70
7 purchase totals =	$919.30		$1,016.0730	$1,016.07	$1,016.10	$1,016.10