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	$53.64	5.439%	$56.5575	$56.56	$56.55	$56.60
Purchase #2	$210.55	10.478%	$232.6114	$232.61	$232.60	$232.60
Purchase #3	$208.76	4.849%	$218.8828	$218.88	$218.90	$218.90
Purchase #4	$199.84	3.112%	$206.059	$206.06	$206.05	$206.10
Purchase #5	$250.67	11.702%	$280.0034	$280.00	$280.00	$280.00
Purchase #6	$63.94	10.326%	$70.5424	$70.54	$70.55	$70.50
Purchase #7	$211.91	5.119%	$222.7577	$222.76	$222.75	$222.80
7 purchase totals =	$1,199.31		$1,287.4142	$1,287.41	$1,287.40	$1,287.50