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	$174.82	3.794%	$181.4527	$181.45	$181.45	$181.50
Purchase #2	$43.88	8.617%	$47.6611	$47.66	$47.65	$47.70
Purchase #3	$127.35	3.206%	$131.4328	$131.43	$131.45	$131.40
Purchase #4	$225.72	12.769%	$254.5422	$254.54	$254.55	$254.50
Purchase #5	$206.48	9.319%	$225.7219	$225.72	$225.70	$225.70
Purchase #6	$219.40	13.254%	$248.4793	$248.48	$248.50	$248.50
Purchase #7	$73.51	9.613%	$80.5765	$80.58	$80.60	$80.60
7 purchase totals =	$1,071.16		$1,169.8665	$1,169.86	$1,169.90	$1,169.90