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	$109.93	7.584%	$118.2671	$118.27	$118.25	$118.30
Purchase #2	$51.74	10.871%	$57.3647	$57.36	$57.35	$57.40
Purchase #3	$55.62	12.292%	$62.4568	$62.46	$62.45	$62.50
Purchase #4	$243.43	7.315%	$261.2369	$261.24	$261.25	$261.20
Purchase #5	$226.43	8.404%	$245.4592	$245.46	$245.45	$245.50
Purchase #6	$224.52	8.442%	$243.474	$243.47	$243.45	$243.50
Purchase #7	$102.77	8.583%	$111.5907	$111.59	$111.60	$111.60
7 purchase totals =	$1,014.44		$1,099.8494	$1,099.85	$1,099.80	$1,100.00