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	$209.71	7.438%	$225.3082	$225.31	$225.30	$225.30
Purchase #2	$38.52	11.252%	$42.8543	$42.85	$42.85	$42.90
Purchase #3	$166.94	4.589%	$174.6009	$174.60	$174.60	$174.60
Purchase #4	$121.78	9.447%	$133.2846	$133.28	$133.30	$133.30
Purchase #5	$111.58	3.496%	$115.4808	$115.48	$115.50	$115.50
Purchase #6	$207.39	5.264%	$218.307	$218.31	$218.30	$218.30
Purchase #7	$135.42	6.560%	$144.3036	$144.30	$144.30	$144.30
7 purchase totals =	$991.34		$1,054.1394	$1,054.13	$1,054.15	$1,054.20