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	$179.96	9.149%	$196.4245	$196.42	$196.40	$196.40
Purchase #2	$178.92	6.149%	$189.9218	$189.92	$189.90	$189.90
Purchase #3	$197.83	12.745%	$223.0434	$223.04	$223.05	$223.00
Purchase #4	$34.57	10.469%	$38.1891	$38.19	$38.20	$38.20
Purchase #5	$146.56	13.611%	$166.5083	$166.51	$166.50	$166.50
Purchase #6	$83.56	10.393%	$92.2444	$92.24	$92.25	$92.20
Purchase #7	$217.36	5.138%	$228.528	$228.53	$228.55	$228.50
7 purchase totals =	$1,038.76		$1,134.8595	$1,134.85	$1,134.85	$1,134.70