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	$66.99	7.309%	$71.8863	$71.89	$71.90	$71.90
Purchase #2	$141.66	10.110%	$155.9818	$155.98	$156.00	$156.00
Purchase #3	$99.81	11.848%	$111.6355	$111.64	$111.65	$111.60
Purchase #4	$187.72	9.469%	$205.4952	$205.50	$205.50	$205.50
Purchase #5	$56.89	9.353%	$62.2109	$62.21	$62.20	$62.20
Purchase #6	$196.51	10.316%	$216.782	$216.78	$216.80	$216.80
Purchase #7	$9.30	10.402%	$10.2674	$10.27	$10.25	$10.30
7 purchase totals =	$758.88		$834.2591	$834.27	$834.30	$834.30