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	$215.61	13.284%	$244.2516	$244.25	$244.25	$244.30
Purchase #2	$192.69	9.789%	$211.5524	$211.55	$211.55	$211.60
Purchase #3	$139.81	9.104%	$152.5383	$152.54	$152.55	$152.50
Purchase #4	$85.52	11.490%	$95.3462	$95.35	$95.35	$95.30
Purchase #5	$26.52	7.371%	$28.4748	$28.47	$28.45	$28.50
Purchase #6	$95.61	9.202%	$104.408	$104.41	$104.40	$104.40
Purchase #7	$28.86	9.123%	$31.4929	$31.49	$31.50	$31.50
7 purchase totals =	$784.62		$868.0642	$868.06	$868.05	$868.10