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	$62.55	13.285%	$70.8598	$70.86	$70.85	$70.90
Purchase #2	$151.43	9.766%	$166.2187	$166.22	$166.20	$166.20
Purchase #3	$97.85	13.645%	$111.2016	$111.20	$111.20	$111.20
Purchase #4	$36.46	3.781%	$37.8386	$37.84	$37.85	$37.80
Purchase #5	$150.52	12.531%	$169.3817	$169.38	$169.40	$169.40
Purchase #6	$164.87	4.231%	$171.8456	$171.85	$171.85	$171.80
Purchase #7	$207.38	8.854%	$225.7414	$225.74	$225.75	$225.70
7 purchase totals =	$871.06		$953.0874	$953.09	$953.10	$953.00