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	$233.28	11.758%	$260.7091	$260.71	$260.70	$260.70
Purchase #2	$188.46	4.192%	$196.3602	$196.36	$196.35	$196.40
Purchase #3	$180.65	7.375%	$193.9729	$193.97	$193.95	$194.00
Purchase #4	$95.25	9.508%	$104.3064	$104.31	$104.30	$104.30
Purchase #5	$28.97	8.274%	$31.367	$31.37	$31.35	$31.40
Purchase #6	$119.83	13.799%	$136.3653	$136.37	$136.35	$136.40
Purchase #7	$82.59	4.445%	$86.2611	$86.26	$86.25	$86.30
7 purchase totals =	$929.03		$1,009.3420	$1,009.35	$1,009.25	$1,009.50