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	$220.75	3.494%	$228.463	$228.46	$228.45	$228.50
Purchase #2	$249.38	12.524%	$280.6124	$280.61	$280.60	$280.60
Purchase #3	$14.77	5.460%	$15.5764	$15.58	$15.60	$15.60
Purchase #4	$139.26	13.336%	$157.8317	$157.83	$157.85	$157.80
Purchase #5	$99.51	12.403%	$111.8522	$111.85	$111.85	$111.90
Purchase #6	$144.25	4.270%	$150.4095	$150.41	$150.40	$150.40
Purchase #7	$59.81	6.507%	$63.7018	$63.70	$63.70	$63.70
7 purchase totals =	$927.73		$1,008.4470	$1,008.44	$1,008.45	$1,008.50