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	$147.44	5.137%	$155.014	$155.01	$155.00	$155.00
Purchase #2	$170.80	6.557%	$181.9994	$182.00	$182.00	$182.00
Purchase #3	$38.57	11.124%	$42.8605	$42.86	$42.85	$42.90
Purchase #4	$137.80	12.172%	$154.573	$154.57	$154.55	$154.60
Purchase #5	$208.34	13.219%	$235.8805	$235.88	$235.90	$235.90
Purchase #6	$164.40	10.448%	$181.5765	$181.58	$181.60	$181.60
Purchase #7	$150.52	7.793%	$162.25	$162.25	$162.25	$162.30
7 purchase totals =	$1,017.87		$1,114.1539	$1,114.15	$1,114.15	$1,114.30