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	$227.37	4.873%	$238.4497	$238.45	$238.45	$238.40
Purchase #2	$149.68	7.850%	$161.4299	$161.43	$161.45	$161.40
Purchase #3	$100.47	10.792%	$111.3127	$111.31	$111.30	$111.30
Purchase #4	$217.28	12.284%	$243.9707	$243.97	$243.95	$244.00
Purchase #5	$114.47	7.627%	$123.2006	$123.20	$123.20	$123.20
Purchase #6	$196.64	13.409%	$223.0075	$223.01	$223.00	$223.00
Purchase #7	$16.71	4.235%	$17.4177	$17.42	$17.40	$17.40
7 purchase totals =	$1,022.62		$1,118.7888	$1,118.79	$1,118.75	$1,118.70