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	$200.40	12.306%	$225.0612	$225.06	$225.05	$225.10
Purchase #2	$76.80	10.431%	$84.811	$84.81	$84.80	$84.80
Purchase #3	$183.90	6.863%	$196.5211	$196.52	$196.50	$196.50
Purchase #4	$179.78	6.122%	$190.7861	$190.79	$190.80	$190.80
Purchase #5	$16.30	7.182%	$17.4707	$17.47	$17.45	$17.50
Purchase #6	$148.39	3.870%	$154.1327	$154.13	$154.15	$154.10
Purchase #7	$164.76	8.748%	$179.1732	$179.17	$179.15	$179.20
7 purchase totals =	$970.33		$1,047.9560	$1,047.95	$1,047.90	$1,048.00