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	$53.43	10.798%	$59.1994	$59.20	$59.20	$59.20
Purchase #2	$64.44	12.202%	$72.303	$72.30	$72.30	$72.30
Purchase #3	$85.67	7.272%	$91.8999	$91.90	$91.90	$91.90
Purchase #4	$28.68	5.617%	$30.291	$30.29	$30.30	$30.30
Purchase #5	$137.90	4.813%	$144.5371	$144.54	$144.55	$144.50
Purchase #6	$56.69	12.558%	$63.8091	$63.81	$63.80	$63.80
Purchase #7	$53.30	3.240%	$55.0269	$55.03	$55.05	$55.00
7 purchase totals =	$480.11		$517.0664	$517.07	$517.10	$517.00