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	$52.99	11.487%	$59.077	$59.08	$59.10	$59.10
Purchase #2	$143.60	6.358%	$152.7301	$152.73	$152.75	$152.70
Purchase #3	$38.86	12.810%	$43.838	$43.84	$43.85	$43.80
Purchase #4	$221.86	10.497%	$245.1486	$245.15	$245.15	$245.10
Purchase #5	$94.34	8.406%	$102.2702	$102.27	$102.25	$102.30
Purchase #6	$164.91	11.741%	$184.2721	$184.27	$184.25	$184.30
Purchase #7	$198.44	11.860%	$221.975	$221.98	$222.00	$222.00
7 purchase totals =	$915.00		$1,009.3110	$1,009.32	$1,009.35	$1,009.30