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	$130.36	4.685%	$136.4674	$136.47	$136.45	$136.50
Purchase #2	$215.38	5.866%	$228.0142	$228.01	$228.00	$228.00
Purchase #3	$174.93	4.262%	$182.3855	$182.39	$182.40	$182.40
Purchase #4	$121.58	12.552%	$136.8407	$136.84	$136.85	$136.80
Purchase #5	$210.55	3.312%	$217.5234	$217.52	$217.50	$217.50
Purchase #6	$133.31	4.482%	$139.285	$139.29	$139.30	$139.30
Purchase #7	$67.44	7.404%	$72.4333	$72.43	$72.45	$72.40
7 purchase totals =	$1,053.55		$1,112.9495	$1,112.95	$1,112.95	$1,112.90