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	$208.32	6.741%	$222.3629	$222.36	$222.35	$222.40
Purchase #2	$241.80	4.687%	$253.1332	$253.13	$253.15	$253.10
Purchase #3	$73.53	12.286%	$82.5639	$82.56	$82.55	$82.60
Purchase #4	$231.50	11.219%	$257.472	$257.47	$257.45	$257.50
Purchase #5	$218.64	4.605%	$228.7084	$228.71	$228.70	$228.70
Purchase #6	$215.29	5.858%	$227.9017	$227.90	$227.90	$227.90
Purchase #7	$166.38	5.454%	$175.4544	$175.45	$175.45	$175.50
7 purchase totals =	$1,355.46		$1,447.5965	$1,447.58	$1,447.55	$1,447.70