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	$214.61	3.391%	$221.8874	$221.89	$221.90	$221.90
Purchase #2	$51.97	13.874%	$59.1803	$59.18	$59.20	$59.20
Purchase #3	$69.88	8.139%	$75.5675	$75.57	$75.55	$75.60
Purchase #4	$86.87	13.179%	$98.3186	$98.32	$98.30	$98.30
Purchase #5	$221.67	12.362%	$249.0728	$249.07	$249.05	$249.10
Purchase #6	$246.90	13.640%	$280.5772	$280.58	$280.60	$280.60
Purchase #7	$52.49	13.385%	$59.5158	$59.52	$59.50	$59.50
7 purchase totals =	$944.39		$1,044.1196	$1,044.13	$1,044.10	$1,044.20