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	$134.41	8.372%	$145.6628	$145.66	$145.65	$145.70
Purchase #2	$133.53	6.496%	$142.2041	$142.20	$142.20	$142.20
Purchase #3	$177.95	10.432%	$196.5137	$196.51	$196.50	$196.50
Purchase #4	$68.59	9.185%	$74.89	$74.89	$74.90	$74.90
Purchase #5	$62.90	3.779%	$65.277	$65.28	$65.30	$65.30
Purchase #6	$68.69	13.597%	$78.0298	$78.03	$78.05	$78.00
Purchase #7	$47.51	4.329%	$49.5667	$49.57	$49.55	$49.60
7 purchase totals =	$693.58		$752.1441	$752.14	$752.15	$752.20