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	$85.95	4.250%	$89.6029	$89.60	$89.60	$89.60
Purchase #2	$236.96	3.640%	$245.5853	$245.59	$245.60	$245.60
Purchase #3	$78.37	6.679%	$83.6043	$83.60	$83.60	$83.60
Purchase #4	$143.63	4.433%	$149.9971	$150.00	$150.00	$150.00
Purchase #5	$247.45	10.348%	$273.0561	$273.06	$273.05	$273.10
Purchase #6	$8.25	4.310%	$8.6056	$8.61	$8.60	$8.60
Purchase #7	$183.68	4.184%	$191.3652	$191.37	$191.35	$191.40
7 purchase totals =	$984.29		$1,041.8165	$1,041.83	$1,041.80	$1,041.90