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	$150.43	11.850%	$168.256	$168.26	$168.25	$168.30
Purchase #2	$183.81	12.369%	$206.5455	$206.55	$206.55	$206.50
Purchase #3	$157.59	10.573%	$174.252	$174.25	$174.25	$174.30
Purchase #4	$85.58	9.254%	$93.4996	$93.50	$93.50	$93.50
Purchase #5	$28.35	11.417%	$31.5867	$31.59	$31.60	$31.60
Purchase #6	$97.97	13.110%	$110.8139	$110.81	$110.80	$110.80
Purchase #7	$205.38	12.510%	$231.073	$231.07	$231.05	$231.10
7 purchase totals =	$909.11		$1,016.0267	$1,016.03	$1,016.00	$1,016.10