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	$80.56	3.754%	$83.5842	$83.58	$83.60	$83.60
Purchase #2	$51.54	12.590%	$58.0289	$58.03	$58.05	$58.00
Purchase #3	$194.43	6.172%	$206.4302	$206.43	$206.45	$206.40
Purchase #4	$220.56	9.450%	$241.4029	$241.40	$241.40	$241.40
Purchase #5	$198.33	6.638%	$211.4951	$211.50	$211.50	$211.50
Purchase #6	$77.61	11.191%	$86.2953	$86.30	$86.30	$86.30
Purchase #7	$192.72	3.501%	$199.4671	$199.47	$199.45	$199.50
7 purchase totals =	$1,015.75		$1,086.7037	$1,086.71	$1,086.75	$1,086.70