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	$52.45	3.606%	$54.3413	$54.34	$54.35	$54.30
Purchase #2	$172.50	8.822%	$187.718	$187.72	$187.70	$187.70
Purchase #3	$85.50	4.760%	$89.5698	$89.57	$89.55	$89.60
Purchase #4	$117.71	10.666%	$130.2649	$130.26	$130.25	$130.30
Purchase #5	$182.47	11.795%	$203.9923	$203.99	$204.00	$204.00
Purchase #6	$30.80	11.257%	$34.2672	$34.27	$34.25	$34.30
Purchase #7	$52.92	6.540%	$56.381	$56.38	$56.40	$56.40
7 purchase totals =	$694.35		$756.5345	$756.53	$756.50	$756.60