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	$49.88	7.656%	$53.6988	$53.70	$53.70	$53.70
Purchase #2	$152.98	7.569%	$164.5591	$164.56	$164.55	$164.60
Purchase #3	$107.39	3.503%	$111.1519	$111.15	$111.15	$111.20
Purchase #4	$157.59	8.744%	$171.3697	$171.37	$171.35	$171.40
Purchase #5	$52.58	7.752%	$56.656	$56.66	$56.65	$56.70
Purchase #6	$10.87	9.364%	$11.8879	$11.89	$11.90	$11.90
Purchase #7	$83.42	6.566%	$88.8974	$88.90	$88.90	$88.90
7 purchase totals =	$614.71		$658.2208	$658.23	$658.20	$658.40