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	$197.41	13.293%	$223.6517	$223.65	$223.65	$223.70
Purchase #2	$249.46	12.248%	$280.0139	$280.01	$280.00	$280.00
Purchase #3	$175.86	12.214%	$197.3395	$197.34	$197.35	$197.30
Purchase #4	$194.38	9.193%	$212.2494	$212.25	$212.25	$212.20
Purchase #5	$185.35	12.443%	$208.4131	$208.41	$208.40	$208.40
Purchase #6	$178.47	12.529%	$200.8305	$200.83	$200.85	$200.80
Purchase #7	$73.34	5.128%	$77.1009	$77.10	$77.10	$77.10
7 purchase totals =	$1,254.27		$1,399.5990	$1,399.59	$1,399.60	$1,399.50