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	$22.28	13.304%	$25.2441	$25.24	$25.25	$25.20
Purchase #2	$243.73	9.373%	$266.5748	$266.57	$266.55	$266.60
Purchase #3	$41.72	5.176%	$43.8794	$43.88	$43.90	$43.90
Purchase #4	$93.85	10.577%	$103.7765	$103.78	$103.80	$103.80
Purchase #5	$138.89	8.869%	$151.2082	$151.21	$151.20	$151.20
Purchase #6	$186.83	7.560%	$200.9543	$200.95	$200.95	$201.00
Purchase #7	$54.77	5.573%	$57.8223	$57.82	$57.80	$57.80
7 purchase totals =	$782.07		$849.4596	$849.45	$849.45	$849.50