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	$54.70	3.538%	$56.6353	$56.64	$56.65	$56.60
Purchase #2	$18.92	8.362%	$20.5021	$20.50	$20.50	$20.50
Purchase #3	$217.77	6.466%	$231.851	$231.85	$231.85	$231.90
Purchase #4	$179.54	9.329%	$196.2893	$196.29	$196.30	$196.30
Purchase #5	$164.75	11.854%	$184.2795	$184.28	$184.30	$184.30
Purchase #6	$220.34	6.833%	$235.3958	$235.40	$235.40	$235.40
Purchase #7	$188.72	7.447%	$202.774	$202.77	$202.75	$202.80
7 purchase totals =	$1,044.74		$1,127.7270	$1,127.73	$1,127.75	$1,127.80