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	$196.57	11.847%	$219.8576	$219.86	$219.85	$219.90
Purchase #2	$191.37	13.709%	$217.6049	$217.60	$217.60	$217.60
Purchase #3	$173.76	9.223%	$189.7859	$189.79	$189.80	$189.80
Purchase #4	$90.66	12.751%	$102.2201	$102.22	$102.20	$102.20
Purchase #5	$167.47	13.599%	$190.2442	$190.24	$190.25	$190.20
Purchase #6	$230.47	8.656%	$250.4195	$250.42	$250.40	$250.40
Purchase #7	$101.98	8.381%	$110.5269	$110.53	$110.55	$110.50
7 purchase totals =	$1,152.28		$1,280.6591	$1,280.66	$1,280.65	$1,280.60