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	$196.44	10.431%	$216.9307	$216.93	$216.95	$216.90
Purchase #2	$32.43	8.786%	$35.2793	$35.28	$35.30	$35.30
Purchase #3	$143.87	10.118%	$158.4268	$158.43	$158.45	$158.40
Purchase #4	$189.47	8.659%	$205.8762	$205.88	$205.90	$205.90
Purchase #5	$199.64	10.751%	$221.1033	$221.10	$221.10	$221.10
Purchase #6	$144.89	6.265%	$153.9674	$153.97	$153.95	$154.00
Purchase #7	$196.49	6.119%	$208.5132	$208.51	$208.50	$208.50
7 purchase totals =	$1,103.23		$1,200.0969	$1,200.10	$1,200.15	$1,200.10