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	$156.25	11.475%	$174.1797	$174.18	$174.20	$174.20
Purchase #2	$123.70	8.522%	$134.2417	$134.24	$134.25	$134.20
Purchase #3	$196.37	5.189%	$206.5596	$206.56	$206.55	$206.60
Purchase #4	$119.41	9.762%	$131.0668	$131.07	$131.05	$131.10
Purchase #5	$69.98	3.514%	$72.4391	$72.44	$72.45	$72.40
Purchase #6	$100.62	4.772%	$105.4216	$105.42	$105.40	$105.40
Purchase #7	$161.80	10.738%	$179.1741	$179.17	$179.15	$179.20
7 purchase totals =	$928.13		$1,003.0826	$1,003.08	$1,003.05	$1,003.10