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	$84.59	5.529%	$89.267	$89.27	$89.25	$89.30
Purchase #2	$82.77	8.598%	$89.8866	$89.89	$89.90	$89.90
Purchase #3	$105.67	13.214%	$119.6332	$119.63	$119.65	$119.60
Purchase #4	$240.80	12.758%	$271.5213	$271.52	$271.50	$271.50
Purchase #5	$207.67	13.704%	$236.1291	$236.13	$236.15	$236.10
Purchase #6	$206.64	10.674%	$228.6968	$228.70	$228.70	$228.70
Purchase #7	$103.53	6.855%	$110.627	$110.63	$110.65	$110.60
7 purchase totals =	$1,031.67		$1,145.7610	$1,145.77	$1,145.80	$1,145.70