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	$52.93	11.755%	$59.1519	$59.15	$59.15	$59.20
Purchase #2	$160.95	13.598%	$182.836	$182.84	$182.85	$182.80
Purchase #3	$84.87	5.716%	$89.7212	$89.72	$89.70	$89.70
Purchase #4	$35.39	7.389%	$38.005	$38.01	$38.00	$38.00
Purchase #5	$154.38	12.864%	$174.2394	$174.24	$174.25	$174.20
Purchase #6	$242.82	8.276%	$262.9158	$262.92	$262.90	$262.90
Purchase #7	$184.73	9.384%	$202.0651	$202.07	$202.05	$202.10
7 purchase totals =	$916.07		$1,008.9344	$1,008.95	$1,008.90	$1,008.90