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	$165.99	8.839%	$180.6619	$180.66	$180.65	$180.70
Purchase #2	$102.90	8.655%	$111.806	$111.81	$111.80	$111.80
Purchase #3	$216.94	9.430%	$237.3974	$237.40	$237.40	$237.40
Purchase #4	$47.96	3.288%	$49.5369	$49.54	$49.55	$49.50
Purchase #5	$39.51	7.155%	$42.3369	$42.34	$42.35	$42.30
Purchase #6	$42.52	11.538%	$47.426	$47.43	$47.45	$47.40
Purchase #7	$119.51	6.681%	$127.4945	$127.49	$127.50	$127.50
7 purchase totals =	$735.33		$796.6596	$796.67	$796.70	$796.60