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	$188.64	6.533%	$200.9639	$200.96	$200.95	$201.00
Purchase #2	$247.85	13.226%	$280.6306	$280.63	$280.65	$280.60
Purchase #3	$212.45	4.333%	$221.6555	$221.66	$221.65	$221.70
Purchase #4	$233.29	3.447%	$241.3315	$241.33	$241.35	$241.30
Purchase #5	$192.42	12.804%	$217.0575	$217.06	$217.05	$217.10
Purchase #6	$43.82	3.631%	$45.4111	$45.41	$45.40	$45.40
Purchase #7	$74.59	10.620%	$82.5115	$82.51	$82.50	$82.50
7 purchase totals =	$1,193.06		$1,289.5616	$1,289.56	$1,289.55	$1,289.60