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	$163.54	9.364%	$178.8539	$178.85	$178.85	$178.90
Purchase #2	$206.53	12.257%	$231.8444	$231.84	$231.85	$231.80
Purchase #3	$57.62	8.798%	$62.6894	$62.69	$62.70	$62.70
Purchase #4	$179.25	9.465%	$196.216	$196.22	$196.20	$196.20
Purchase #5	$200.44	11.182%	$222.8532	$222.85	$222.85	$222.90
Purchase #6	$13.58	5.412%	$14.3149	$14.31	$14.30	$14.30
Purchase #7	$166.89	4.852%	$174.9875	$174.99	$175.00	$175.00
7 purchase totals =	$987.85		$1,081.7593	$1,081.75	$1,081.75	$1,081.80