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	$213.96	9.134%	$233.5031	$233.50	$233.50	$233.50
Purchase #2	$112.46	5.646%	$118.8095	$118.81	$118.80	$118.80
Purchase #3	$172.98	12.453%	$194.5212	$194.52	$194.50	$194.50
Purchase #4	$74.82	8.342%	$81.0615	$81.06	$81.05	$81.10
Purchase #5	$185.45	9.718%	$203.472	$203.47	$203.45	$203.50
Purchase #6	$37.52	10.632%	$41.5091	$41.51	$41.50	$41.50
Purchase #7	$135.71	10.259%	$149.6325	$149.63	$149.65	$149.60
7 purchase totals =	$932.90		$1,022.5089	$1,022.50	$1,022.45	$1,022.50