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	$108.52	3.378%	$112.1858	$112.19	$112.20	$112.20
Purchase #2	$147.37	7.321%	$158.159	$158.16	$158.15	$158.20
Purchase #3	$216.33	7.842%	$233.2946	$233.29	$233.30	$233.30
Purchase #4	$141.65	7.238%	$151.9026	$151.90	$151.90	$151.90
Purchase #5	$217.41	3.762%	$225.589	$225.59	$225.60	$225.60
Purchase #6	$17.95	3.430%	$18.5657	$18.57	$18.55	$18.60
Purchase #7	$102.58	5.404%	$108.1234	$108.12	$108.10	$108.10
7 purchase totals =	$951.81		$1,007.8201	$1,007.82	$1,007.80	$1,007.90