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	$103.71	9.268%	$113.3218	$113.32	$113.30	$113.30
Purchase #2	$7.41	8.708%	$8.0553	$8.06	$8.05	$8.10
Purchase #3	$111.87	10.402%	$123.5067	$123.51	$123.50	$123.50
Purchase #4	$141.92	12.367%	$159.4712	$159.47	$159.45	$159.50
Purchase #5	$131.96	3.857%	$137.0497	$137.05	$137.05	$137.00
Purchase #6	$160.94	4.803%	$168.6699	$168.67	$168.65	$168.70
Purchase #7	$172.30	10.737%	$190.7999	$190.80	$190.80	$190.80
7 purchase totals =	$830.11		$900.8745	$900.88	$900.80	$900.90