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	$131.32	8.538%	$142.5321	$142.53	$142.55	$142.50
Purchase #2	$73.86	13.158%	$83.5785	$83.58	$83.60	$83.60
Purchase #3	$153.88	3.336%	$159.0134	$159.01	$159.00	$159.00
Purchase #4	$205.51	13.266%	$232.773	$232.77	$232.75	$232.80
Purchase #5	$232.55	9.810%	$255.3632	$255.36	$255.35	$255.40
Purchase #6	$196.57	12.331%	$220.809	$220.81	$220.80	$220.80
Purchase #7	$11.89	3.179%	$12.268	$12.27	$12.25	$12.30
7 purchase totals =	$1,005.58		$1,106.3372	$1,106.33	$1,106.30	$1,106.40