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	$75.38	10.839%	$83.5504	$83.55	$83.55	$83.60
Purchase #2	$163.71	5.236%	$172.2819	$172.28	$172.30	$172.30
Purchase #3	$199.59	9.805%	$219.1598	$219.16	$219.15	$219.20
Purchase #4	$182.90	6.444%	$194.6861	$194.69	$194.70	$194.70
Purchase #5	$218.31	4.412%	$227.9418	$227.94	$227.95	$227.90
Purchase #6	$136.99	4.433%	$143.0628	$143.06	$143.05	$143.10
Purchase #7	$141.82	12.419%	$159.4326	$159.43	$159.45	$159.40
7 purchase totals =	$1,118.70		$1,200.1154	$1,200.11	$1,200.15	$1,200.20