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	$70.95	10.419%	$78.3423	$78.34	$78.35	$78.30
Purchase #2	$219.51	4.553%	$229.5043	$229.50	$229.50	$229.50
Purchase #3	$44.73	7.132%	$47.9201	$47.92	$47.90	$47.90
Purchase #4	$26.35	4.372%	$27.502	$27.50	$27.50	$27.50
Purchase #5	$170.30	11.744%	$190.3	$190.30	$190.30	$190.30
Purchase #6	$24.32	5.166%	$25.5764	$25.58	$25.60	$25.60
Purchase #7	$16.84	12.486%	$18.9426	$18.94	$18.95	$18.90
7 purchase totals =	$573.00		$618.0877	$618.08	$618.10	$618.00