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	$161.38	6.627%	$172.0747	$172.07	$172.05	$172.10
Purchase #2	$80.61	5.325%	$84.9025	$84.90	$84.90	$84.90
Purchase #3	$241.39	5.410%	$254.4492	$254.45	$254.45	$254.40
Purchase #4	$162.54	5.827%	$172.0112	$172.01	$172.00	$172.00
Purchase #5	$100.59	11.129%	$111.7847	$111.78	$111.80	$111.80
Purchase #6	$158.52	6.646%	$169.0552	$169.06	$169.05	$169.10
Purchase #7	$42.69	5.802%	$45.1669	$45.17	$45.15	$45.20
7 purchase totals =	$947.72		$1,009.4444	$1,009.44	$1,009.40	$1,009.50