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	$196.89	5.796%	$208.3017	$208.30	$208.30	$208.30
Purchase #2	$74.66	10.617%	$82.5867	$82.59	$82.60	$82.60
Purchase #3	$151.62	9.750%	$166.403	$166.40	$166.40	$166.40
Purchase #4	$160.50	12.834%	$181.0986	$181.10	$181.10	$181.10
Purchase #5	$204.53	11.638%	$228.3332	$228.33	$228.35	$228.30
Purchase #6	$200.90	4.567%	$210.0751	$210.08	$210.10	$210.10
Purchase #7	$5.62	13.589%	$6.3837	$6.38	$6.40	$6.40
7 purchase totals =	$994.72		$1,083.1820	$1,083.18	$1,083.25	$1,083.20