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	$152.83	4.198%	$159.2458	$159.25	$159.25	$159.20
Purchase #2	$115.94	7.790%	$124.9717	$124.97	$124.95	$125.00
Purchase #3	$56.55	8.472%	$61.3409	$61.34	$61.35	$61.30
Purchase #4	$38.51	12.870%	$43.4662	$43.47	$43.45	$43.50
Purchase #5	$240.51	5.579%	$253.9281	$253.93	$253.95	$253.90
Purchase #6	$127.46	3.185%	$131.5196	$131.52	$131.50	$131.50
Purchase #7	$238.74	11.748%	$266.7872	$266.79	$266.80	$266.80
7 purchase totals =	$970.54		$1,041.2595	$1,041.27	$1,041.25	$1,041.20