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	$55.74	6.871%	$59.5699	$59.57	$59.55	$59.60
Purchase #2	$70.88	5.436%	$74.733	$74.73	$74.75	$74.70
Purchase #3	$156.52	8.284%	$169.4861	$169.49	$169.50	$169.50
Purchase #4	$184.95	6.465%	$196.907	$196.91	$196.90	$196.90
Purchase #5	$78.41	7.665%	$84.4201	$84.42	$84.40	$84.40
Purchase #6	$94.39	6.418%	$100.448	$100.45	$100.45	$100.40
Purchase #7	$208.52	12.740%	$235.0854	$235.09	$235.10	$235.10
7 purchase totals =	$849.41		$920.6495	$920.66	$920.65	$920.60