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	$192.99	11.171%	$214.5489	$214.55	$214.55	$214.50
Purchase #2	$72.96	8.132%	$78.8931	$78.89	$78.90	$78.90
Purchase #3	$42.97	10.718%	$47.5755	$47.58	$47.60	$47.60
Purchase #4	$88.83	12.360%	$99.8094	$99.81	$99.80	$99.80
Purchase #5	$33.41	4.304%	$34.848	$34.85	$34.85	$34.80
Purchase #6	$65.52	6.537%	$69.803	$69.80	$69.80	$69.80
Purchase #7	$200.88	6.688%	$214.3149	$214.31	$214.30	$214.30
7 purchase totals =	$697.56		$759.7928	$759.79	$759.80	$759.70