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	$113.89	9.790%	$125.0398	$125.04	$125.05	$125.00
Purchase #2	$43.73	4.741%	$45.8032	$45.80	$45.80	$45.80
Purchase #3	$164.28	7.636%	$176.8244	$176.82	$176.80	$176.80
Purchase #4	$167.69	7.122%	$179.6329	$179.63	$179.65	$179.60
Purchase #5	$38.69	9.467%	$42.3528	$42.35	$42.35	$42.40
Purchase #6	$75.71	9.339%	$82.7806	$82.78	$82.80	$82.80
Purchase #7	$118.25	4.639%	$123.7356	$123.74	$123.75	$123.70
7 purchase totals =	$722.24		$776.1693	$776.16	$776.20	$776.10