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	$172.52	4.666%	$180.5698	$180.57	$180.55	$180.60
Purchase #2	$191.46	8.674%	$208.0672	$208.07	$208.05	$208.10
Purchase #3	$139.60	11.641%	$155.8508	$155.85	$155.85	$155.90
Purchase #4	$139.82	3.798%	$145.1304	$145.13	$145.15	$145.10
Purchase #5	$100.78	4.523%	$105.3383	$105.34	$105.35	$105.30
Purchase #6	$219.55	9.492%	$240.3897	$240.39	$240.40	$240.40
Purchase #7	$213.78	13.514%	$242.6702	$242.67	$242.65	$242.70
7 purchase totals =	$1,177.51		$1,278.0164	$1,278.02	$1,278.00	$1,278.10