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	$199.32	3.435%	$206.1666	$206.17	$206.15	$206.20
Purchase #2	$240.46	6.258%	$255.508	$255.51	$255.50	$255.50
Purchase #3	$194.42	8.843%	$211.6126	$211.61	$211.60	$211.60
Purchase #4	$84.66	7.385%	$90.9121	$90.91	$90.90	$90.90
Purchase #5	$98.93	13.613%	$112.3973	$112.40	$112.40	$112.40
Purchase #6	$114.93	7.707%	$123.7877	$123.79	$123.80	$123.80
Purchase #7	$66.57	12.351%	$74.7921	$74.79	$74.80	$74.80
7 purchase totals =	$999.29		$1,075.1764	$1,075.18	$1,075.15	$1,075.20