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	$125.76	12.552%	$141.5454	$141.55	$141.55	$141.50
Purchase #2	$77.53	10.641%	$85.78	$85.78	$85.80	$85.80
Purchase #3	$179.84	7.710%	$193.7057	$193.71	$193.70	$193.70
Purchase #4	$34.54	5.669%	$36.4981	$36.50	$36.50	$36.50
Purchase #5	$229.35	9.102%	$250.2254	$250.23	$250.25	$250.20
Purchase #6	$102.43	3.242%	$105.7508	$105.75	$105.75	$105.80
Purchase #7	$126.68	12.789%	$142.8811	$142.88	$142.90	$142.90
7 purchase totals =	$876.13		$956.3865	$956.40	$956.45	$956.40