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	$210.32	5.231%	$221.3218	$221.32	$221.30	$221.30
Purchase #2	$65.95	13.862%	$75.092	$75.09	$75.10	$75.10
Purchase #3	$105.38	5.688%	$111.374	$111.37	$111.35	$111.40
Purchase #4	$51.50	13.248%	$58.3227	$58.32	$58.30	$58.30
Purchase #5	$135.37	12.713%	$152.5796	$152.58	$152.60	$152.60
Purchase #6	$187.40	4.804%	$196.4027	$196.40	$196.40	$196.40
Purchase #7	$244.40	9.419%	$267.42	$267.42	$267.40	$267.40
7 purchase totals =	$1,000.32		$1,082.5128	$1,082.50	$1,082.45	$1,082.50