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	$135.45	5.484%	$142.8781	$142.88	$142.90	$142.90
Purchase #2	$135.71	13.181%	$153.5979	$153.60	$153.60	$153.60
Purchase #3	$53.70	10.514%	$59.346	$59.35	$59.35	$59.30
Purchase #4	$81.32	10.860%	$90.1514	$90.15	$90.15	$90.20
Purchase #5	$129.54	4.653%	$135.5675	$135.57	$135.55	$135.60
Purchase #6	$240.33	5.437%	$253.3967	$253.40	$253.40	$253.40
Purchase #7	$100.52	13.656%	$114.247	$114.25	$114.25	$114.20
7 purchase totals =	$876.57		$949.1846	$949.20	$949.20	$949.20