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	$149.74	12.359%	$168.2464	$168.25	$168.25	$168.20
Purchase #2	$102.31	11.524%	$114.1002	$114.10	$114.10	$114.10
Purchase #3	$212.42	6.372%	$225.9554	$225.96	$225.95	$226.00
Purchase #4	$124.52	10.139%	$137.1451	$137.15	$137.15	$137.10
Purchase #5	$200.35	12.520%	$225.4338	$225.43	$225.45	$225.40
Purchase #6	$58.94	3.605%	$61.0648	$61.06	$61.05	$61.10
Purchase #7	$157.83	10.583%	$174.5331	$174.53	$174.55	$174.50
7 purchase totals =	$1,006.11		$1,106.4788	$1,106.48	$1,106.50	$1,106.40