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	$101.80	8.606%	$110.5609	$110.56	$110.55	$110.60
Purchase #2	$39.55	8.367%	$42.8591	$42.86	$42.85	$42.90
Purchase #3	$233.87	13.523%	$265.4962	$265.50	$265.50	$265.50
Purchase #4	$62.52	7.323%	$67.0983	$67.10	$67.10	$67.10
Purchase #5	$51.66	9.178%	$56.4014	$56.40	$56.40	$56.40
Purchase #6	$229.72	12.554%	$258.559	$258.56	$258.55	$258.60
Purchase #7	$246.35	11.474%	$274.6162	$274.62	$274.60	$274.60
7 purchase totals =	$965.47		$1,075.5911	$1,075.60	$1,075.55	$1,075.70