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	$221.57	5.118%	$232.91	$232.91	$232.90	$232.90
Purchase #2	$94.42	6.677%	$100.7244	$100.72	$100.70	$100.70
Purchase #3	$142.89	12.459%	$160.6927	$160.69	$160.70	$160.70
Purchase #4	$181.97	7.556%	$195.7197	$195.72	$195.70	$195.70
Purchase #5	$67.46	4.800%	$70.6981	$70.70	$70.70	$70.70
Purchase #6	$217.88	9.672%	$238.9534	$238.95	$238.95	$239.00
Purchase #7	$76.31	13.185%	$86.3715	$86.37	$86.35	$86.40
7 purchase totals =	$1,002.50		$1,086.0698	$1,086.06	$1,086.00	$1,086.10