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	$229.37	4.238%	$239.0907	$239.09	$239.10	$239.10
Purchase #2	$55.45	6.525%	$59.0681	$59.07	$59.05	$59.10
Purchase #3	$158.97	13.275%	$180.0733	$180.07	$180.05	$180.10
Purchase #4	$63.82	13.561%	$72.4746	$72.47	$72.45	$72.50
Purchase #5	$125.73	5.162%	$132.2202	$132.22	$132.20	$132.20
Purchase #6	$168.30	5.353%	$177.3091	$177.31	$177.30	$177.30
Purchase #7	$200.87	6.558%	$214.0431	$214.04	$214.05	$214.00
7 purchase totals =	$1,002.51		$1,074.2791	$1,074.27	$1,074.20	$1,074.30